BEATCALC:  Beat the Calculator!

___________________________________________
Back to Calculation Tips & Tricks
___________________________________________

From the BEATCALC mailing list:
a weekly service from B. Lee Clay, archived here by the Math Forum.
To subscribe to the BEATCALC mailing list, write to BEATCALC@aol.com.


 Squaring Numbers

 Multiplying Numbers

  1. same 1st digit
  2. same 1st digit, sum 10
  3. same 2nd digit
  4. 3 digits, middle 0
  5. 3 digits, middle 1
  6. 3 digits, middle 2
  7. 3 digits, middle 3
  8. 3 digits, middle 4
  9. 3 digits, middle 5
  10. difference of 1
  11. difference of 2
  12. difference of 3
  13. difference of 4
  14. difference of 6
  15. difference of 8
  16. difference of 10
  17. 2 digits by 1 1/25
  18. 2 digits by 1.1
  19. 2 digits by 1 1/9
  20. 2 digits by 1 1/8
  21. 2 digits by 1 1/7
  22. 2 digits by 1 1/6
  23. 2 digits by 1 1/5
  24. 2 digits by 1 2/9
  25. 2 digits by 1 1/4
  26. 2 digits by 1 2/7
  27. 2 digits by 1.3
  28. 2 digits by 1 1/3
  29. 2 digits by 1 3/8
  30. 2 digits by 1 2/5
  31. 2 digits by 1 3/7
  32. 2 digits by 1 1/2
  33. 2 digits by 1 4/7
  34. 2 digits by 1 3/5
  35. 2 digits by 1.6
  36. 2,3 digits by 1 2/3
  37. 2 digits by 1.7
  38. 2 digits by 1 5/7
  39. 2 digits by 1 3/4
  40. 2 digits by 1 4/5
  41. 2 digits by 1 5/6
  42. 2 digits by 1 6/7
  43. 2 digits by 1.9
  44. 2 digits by 2.1
  45. 2 digits by 2 1/9
  46. 2 digits by 2 1/7
  47. 2 digits by 2 1/5
  48. 2 digits by 2 2/9
  49. 2 digits by 2 1/4
  50. 2 digits by 2.3
  51. 2 digits by 2 1/3
  52. 2 digits by 2 3/8
  53. 2 digits by 2 2/5
  54. 2 digits by 2.4
  55. 2 digits by 2 4/9
  56. 2, 3 digits by 2 1/2
  57. 2 digits by 2 4/7
  58. 2 digits by 2.6
  59. 2 digits by 2 5/8
  60. 2 digits by 2 2/3
  61. 2 digits by 2.7
  62. 2 digits by 2 5/7
  63. 2 digits by 2 3/4
  64. 2 digits by 2.8
  65. 2 digits by 2 7/9
  66. 2 digits by 2 6/7
  67. 2 digits by 2.9
  68. 2 digits by 3.1
  69. 2 digits by 3 1/8
  70. 2 digits by 3 1/7
  71. 2 digits by 3 1/6
  72. 2 digits by 3.2
  73. 2 digits by 3 2/9
  74. 2 digits by 3 1/4
  75. 2 digits by 3 1/3
  76. 2 digits by 3.4
  77. 2 digits by 3 3/7
  78. 2 digits by 3 4/9
  79. 2 digits by 3 1/2
  80. 2 digits by 3.6
  81. 2 digits by 3 4/7
  82. 2 digits by 3 5/8
  83. 2 digits by 3 2/3
  84. 2 digits by 3.7
  85. 2 digits by 3 5/7
  86. 2 digits by 3 3/4
  87. 2 digits by 3 4/5
  88. 2 digits by 3 6/7
  89. 2 digits by 3 7/8
  90. 2 digits by 3.9
  91. 2 digits by 4.1
  92. 2 digits by 4 1/4
  93. 2 digits by 4 1/7
  94. 2 digits by 4 1/6
  95. 2 digits by 4 1/5
  96. 2 digits by 4 2/7
  97. 2 digits by 4.3
  98. 2 digits by 4.4
  99. 2 digits by 4 3/7
  100. 2 digits by 4 4/9
  101. 2 digits by 4 1/2
  102. 2 digits by 4 5/9
  103. 2 digits by 4.6
  104. 2 digits by 4.7
  105. 2 digits by 4 3/4
  106. 2 digits by 4 4/5
  107. 2 digits by 4 5/6
  108. 2 digits by 4 7/8
  109. 2 digits by 5.1
  110. 2 digits by 5 1/8
  111. 2 digits by 5 1/6
  112. 2 digits by 5.2
  113. 2 digits by 5 1/4
  114. 2 digits by 5.3
  115. 2 digits by 5 4/9
  116. 2 digits by 5 1/2
  117. 2 digits by 5 5/9
  118. 2 digits by 5.6
  119. 2 digits by 5.7
  120. 2 digits by 5 4/7
  121. 2 digits by 5 5/7
  122. 2 digits by 5 4/5
  123. 2 digits by 5 6/7
  124. 2 digits by 5.9
  125. 2 digits by 6.1
  126. 2 digits by 6 1/8
  127. 2 digits by 6 1/5
  128. 2 digits by 6 1/4
  129. 2 digits by 6.3
  130. 2 digits by 6 1/3
  131. 2 digits by 6 3/8
  132. 2 digits by 6.4
  133. 2 digits by 6 4/9
  134. 2 digits by 6 1/2
  135. 2 digits by 6 5/9
  136. 2 digits by 6.6
  137. 2 digits by 6 2/3
  138. 2 digits by 6 7/9
  139. 2 digits by 6 5/6
  140. 2 digits by 6.8
  141. 2 digits by 6 6/7
  142. 2 digits by 6 8/9
  143. 2 digits by 7.1
  144. 2 digits by 7 1/7
  145. 2 digits by 7.2
  146. 2 digits by 7 1/4
  147. 2 digits by 7.3
  148. 2 digits by 7 2/7
  149. 2 digits by 7.4
  150. 2 digits by 7 1/2
  151. 2 digits by 7 3/5
  152. 2 digits by 7.6
  153. 2 digits by 7.7
  154. 2 digits by 7 3/4
  155. 2 digits by 7 4/5
  156. 2 digits by 8.1
  157. 2 digits by 8 1/6
  158. 2 digits by 8.2
  159. 2 digits by 8 2/7
  160. 2 digits by 8.3
  161. 2 digits by 8 1/3
  162. 2 digits by 8 3/7
  163. 2 digits by 8 4/7
  164. 2 digits by 8 1/2
  165. 2 digits by 8.6
  166. 2 digits by 8 5/8
  167. 2 digits by 8 2/3
  168. 2 digits by 8 5/7
  169. 2 digits by 8 7/9
  170. 2 digits by 8 7/8
  171. 2 digits by 8 8/9
  172. 2 digits by 9.1
  173. 2 digits by 9.2
  174. 2 digits by 9.3
  175. 2 digits by 9 1/3
  176. 2 digits by 9.4
  177. 2 digits by 9 1/2 (four steps)
  178. 2 digits by 9 1/2 (two steps)
  179. 2 digits by 9.6
  180. 2 digits by 9 2/3
  181. 2 digits by 9 5/7
  182. 2 digits by 9.7
  183. 2 digits by 9 3/4
  184. 2 digits by 9 7/9
  185. 2 digits by 9 4/5
  186. 2 digits by 9 5/6
  187. 2 digits by 9 6/7
  188. 2 digits by 9 7/8
  189. 2 digits by 9 8/9
  190. 2 digits by 10.1
  191. 2 digits by 10.4
  192. 2 digits by 10.6
  193. 2 digits by 10.7
  194. 2 digits by 10 1/2
  195. 2 digits by 11 1/2
  196. 2 digits by 12 1/2
  197. 2 digits by 15
  198. 2,3 digits by 16 2/3
  199. 2 digits by 18
  200. 2 digits by 19 1/2
  201. 2 digits by 20 1/2
  202. 2 digits by 21
  203. 2 digits by 22
  204. 2 digits by 23
  205. 2 digits by 24
  206. 2,3 digits by 25
  207. 2 digits by 26
  208. 2 digits by 27
  209. 2 digits by 28
  210. 2 digits by 29
  211. 2 digits by 29 1/2
  212. 2 digits by 30 1/2
  213. 2 digits by 31
  214. 2 digits by 32
  215. 2 digits by 33
  216. 2 digits by 33 1/3
  217. 2 digits by 34
  218. 2 digits by 35
  219. 2 digits by 36
  220. 2 digits by 37
  221. 2 digits by 37 1/2
  222. 2 digits by 38
  223. 2 digits by 39
  224. 2 digits by 39 1/2
  225. 2 digits by 40 1/2
  226. 2 digits by 42
  227. 2 digits by 43
  228. 2 digits by 44
  229. 2 digits by 45
  230. 2 digits by 46
  231. 2 digits by 47
  232. 2 digits by 48
  233. 2 digits by 49 (a)
  234. 2 digits by 49 (b)
  235. 2 digits by 49 1/2
  236. 2 digits by 50 1/2
  237. 2 digits by 51
  238. 2 digits by 52
  239. 2 digits by 53
  240. 2 digits by 54
  241. 2 digits by 55 (a)
  242. 2 digits by 55 (b)
  243. 2 digits by 56
  244. 2 digits by 57
  245. 2 digits by 58
  246. 2 digits by 59
  247. 2 digits by 59 1/2
  248. 2 digits by 60 1/2
  249. 2 digits by 61
  250. 2 digits by 62
  251. 2 digits by 63
  252. 2 digits by 64
  253. 2 digits by 65
  254. 2 digits by 66
  255. 2 digits by 67
  256. 2 digits by 68
  257. 2 digits by 69
  258. 2 digits by 69 1/2
  259. 2 digits by 70 1/2
  260. 2 digits by 71
  261. 2 digits by 72
  262. 2 digits by 73
  263. 2 digits by 74
  264. 2,3 digits by 75
  265. 2 digits by 76
  266. 2 digits by 77
  267. 2 digits by 78
  268. 2 digits by 79
  269. 2 digits by 79 1/2
  270. 2 digits by 80 1/2
  271. 2 digits by 81
  272. 2 digits by 82
  273. 2 digits by 83
  274. 2 digits by 84
  275. 2 digits by 85
  276. 2 digits by 86
  277. 2 digits by 87
  278. 2 digits by 88
  279. 2 digits by 89
  280. 2 digits by 89 1/2
  281. 2 digits by 90 1/2
  282. 2 digits by 91
  283. 2 digits by 92
  284. 2 digits by 93
  285. 2 digits by 94
  286. 2 digits by 97
  287. 2 digits by 98
  288. 2 digits by 99
  289. 3 digits by 99
  290. 2,3 digits by 101
  291. 2 digits by 102 + 11
  292. 2 digits by 103 + 12
  293. 2 digits by 125
  294. 3 digits by 143
  295. 2 digits by 166 2/3
  296. 2 digits by 198
  297. 2 digits by 201 + 11
  298. 2 digits by 202 + 11
  299. 2 digits by 250
  300. 2 digits by 297
  301. 2 digits by 375
  302. 2 digits by 396
  303. 2 digits by 495
  304. 2 digits by 594
  305. 2 digits by 625
  306. 2 digits by 693
  307. 2 digits by 792
  308. 2 digits by 875
  309. 2 digits by 891
  310. 2 digits by 999
  311. 2,3 digits by 1001 + 21,201
  312. 2-4 digits by 1000, + 21, 201, 2001
  313. 2-5 digits by 100001
  314. 1 rep. by 9 rep.
  315. 1 rep. by 12 rep.
  316. 1 rep. by 13 rep.
  317. 1 rep. by 14 rep.
  318. 1 rep. by 15 rep.
  319. 1 rep. by 16 rep.
  320. 1 rep. by 17 rep.
  321. 1 rep. by 18 rep.
  322. 1 rep. by 19 rep.
  323. 1 rep. by 21
  324. 1 rep. by 22
  325. 1 rep. by 23
  326. 1 rep. by 24
  327. 1 rep. by 25
  328. 1 rep. by 26
  329. 1 rep. by 27
  330. 1 rep. by 29
  331. 1 rep. by 33
  332. 1 rep. by 41
  333. 1 rep. by 44
  334. 1 rep. by 45
  335. 1 rep. by 55
  336. 1 rep. by 66
  337. 1 rep. by 77
  338. 1 rep. by 88
  339. 1 rep. by 99
  340. 1 rep. by 222
  341. 1 rep. by 333
  342. 2 rep. by 5 rep.
  343. 2 rep. by 9 rep.
  344. 2 rep. by 12
  345. 2 rep. by 13
  346. 2 rep. by 14
  347. 2 rep. by 15
  348. 2 rep. by 16
  349. 2 rep. by 17
  350. 2 rep. by 22
  351. 2 rep. by 24
  352. 2 rep. by 28
  353. 2 rep. by 33
  354. 2 rep. by 44
  355. 2 rep. by 45
  356. 2 rep. by 55
  357. 2 rep. by 66
  358. 2 rep. by 77
  359. 2 rep. by 88
  360. 2 rep. by 99
  361. 3 rep. by 6 rep.
  362. 3 rep. by 9 rep.
  363. 3 rep. by 13
  364. 3 rep. by 15
  365. 3 rep. by 22
  366. 3 rep. by 23
  367. 3 rep. by 24
  368. 3 rep. by 35
  369. 3 rep. by 55
  370. 3 rep. by 66
  371. 3 rep. by 77
  372. 3 rep. by 88
  373. 3 rep. by 99
  374. 4 rep. by 15
  375. 4 rep. by 17
  376. 4 rep. by 22
  377. 4 rep. by 24
  378. 4 rep. by 28
  379. 4 rep. by 31
  380. 4 rep. by 36
  381. 4 rep. by 42
  382. 4 rep. by 44
  383. 4 rep. by 55
  384. 4 rep. by 66
  385. 4 rep. by 88
  386. 4 rep. by 3 rep.
  387. 4 rep. by 5 rep.
  388. 4 rep. by 9 rep.
  389. 5 rep. by 15
  390. 5 rep. by 25
  391. 5 rep. by 28
  392. 5 rep. by 33
  393. 5 rep. by 55
  394. 5 rep. by 66
  395. 5 rep. by 88
  396. 5 rep. by 9 rep.
  397. 6 rep. by 9 rep.
  398. 6 rep. by 12
  399. 6 rep. by 16
  400. 6 rep. by 22
  401. 6 rep. by 31
  402. 6 rep. by 32
  403. 6 rep. by 33
  404. 6 rep. by 43
  405. 6 rep. by 55
  406. 6 rep. by 66
  407. 6 rep. by 77
  408. 6 rep. by 88
  409. 6 rep. by 444
  410. 6 rep. by 888
  411. 7 rep. by 9 rep.
  412. 7 rep. by 17
  413. 7 rep. by 32
  414. 7 rep. by 33
  415. 7 rep. by 42
  416. 7 rep. by 44
  417. 7 rep. by 55
  418. 7 rep. by 88
  419. 8 rep. by 9 rep.
  420. 8 rep. by 22
  421. 8 rep. by 23
  422. 8 rep. by 24
  423. 8 rep. by 29
  424. 8 rep. by 36
  425. 8 rep. by 44
  426. 8 rep. by 55
  427. 8 rep. by 66
  428. 8 rep. by 88
  429. 9 rep. by 14
  430. 9 rep. by 22
  431. 9 rep. by 25
  432. 9 rep. by 27
  433. 9 rep. by 33
  434. 9 rep. by 44
  435. 9 rep. by 55
  436. 9 rep. by 77
  437. 9 rep. by 99
  438. 3 repeating by 2, /37
  439. 3 repeating by 5, /37
  440. 9 rep. by 3, /12345679
  441. multi-digits by 8 + last digit
  442. by 8, add number, - 20
  443. integer + 1/2 times, + 1
  444. sum,difference of 2,1 digits
  445. two mixed numbers
  446. two mixed numbers,fractions
  447. 4 digits by 99
  448. 4 digits by 137, then 73; -1200
  449. 5 digits by 9091, then 11; -1200

 Dividing Numbers

 Adding Numbers

 Subtracting Numbers

 Finding Percents

Calculation
Practice Exercises

Full List


   Multiplying a 2-digit number by 3 1/2

  1. Select a 2-digit number.
  2. If number is even, divide by 2, then multiply by 7.
  3. If number is odd, multiply by 7, then divide by 2.

   Example:

  1. The 2-digit number chosen to multiply by 3 1/2 is 84.
  2. Divide by 2: 84/2 = 42
  3. Multiply by 7: 42 × 7 = 280 +14 = 294
  4. So 84 × 3 1/2 = 294.

   See the pattern?

  1. The 2-digit number chosen to multiply by 3 1/2 is 63.
  2. Multiply by 7: 63 × 7 = 420 + 21 = 441
  3. Divide by 2: 441/2 = 220.5
  4. So 63 × 3 1/2 = 220.5.


[Privacy Policy] [Terms of Use]

_____________________________________
Home || The Math Library || Quick Reference || Search || Help 
_____________________________________

© 1994-2008 Drexel University. All rights reserved.
http://mathforum.org/
 The Math Forum is a research and educational enterprise of the Drexel School of Education.The Math Forum is a research and educational enterprise of the Drexel School of Education.

18 October 1999
Web page design by Sarah Seastone