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Math Main Page => Exercises - Math III
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Goal: to practise how to make use of distributive property on special numbers, like (A + B) * (A - B) = A*A - B*B, A*C +B*C = (A + B ) *C, A*C - B*C = (A-B) * C
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Thursday March 11 2010
02:57:46 PM | Thursday March 11 2010
02:57:46 PMFlip Answers |
| 1) | 409 * 391 = | | 1) 400 * 400 - 9 * 9 = 159919 |
| 2) | 405 * 395 = | | 2) 400 * 400 - 5 * 5 = 159975 |
| 3) | 209 * 191 = | | 3) 200 * 200 - 9 * 9 = 39919 |
| 4) | 305 * 295 = | | 4) 300 * 300 - 5 * 5 = 89975 |
| 5) | 395 * 405 = | | 5) 400 * 400 - 5 * 5 = 159975 |
| 6) | 93 * 107 = | | 6) 100 * 100 - 7 * 7 = 9951 |
| 7) | 192 * 208 = | | 7) 200 * 200 - 8 * 8 = 39936 |
| 8) | 307 * 293 = | | 8) 300 * 300 - 7 * 7 = 89951 |
| 9) | 202 * 198 = | | 9) 200 * 200 - 2 * 2 = 39996 |
| 10) | 407 * 393 = | | 10) 400 * 400 - 7 * 7 = 159951 |
| 11) | 154 * 97 - 54 * 97 = | | 11) ( 154 - 54) * 97 = 9700 |
| 12) | 43 * 240 - 40 * 43 = | | 12) ( 240 - 40) * 43 = 8600 |
| 13) | 72 * 49 + 72 * 51 = | | 13) ( 49 + 51) * 72 = 7200 |
| 14) | 48 * 72 + 72 * 52 = | | 14) ( 52 + 48) * 72 = 7200 |
| 15) | 271 * 78 - 71 * 78 = | | 15) ( 271 - 71) * 78 = 15600 |
| 16) | 67 * 57 + 67 * 143 = | | 16) ( 143 + 57) * 67 = 13400 |
| 17) | 75 * 37 + 25 * 37 = | | 17) ( 25 + 75) * 37 = 3700 |
| 18) | 38 * 37 + 62 * 37 = | | 18) ( 62 + 38) * 37 = 3700 |
| 19) | 75 * 38 + 62 * 75 = | | 19) ( 38 + 62) * 75 = 7500 |
| 20) | 77 * 152 + 77 * 48 = | | 20) ( 152 + 48) * 77 = 15400 |
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Score: ______________ | |
