Basic Simplification Quiz Set 009

This is a multiplication by a number that contains 9 only. Proceed like this: 488 × 99 = 488 × (100 - 1) = 488 × 100 - 488 = 48800 - 488 = 48312.

This is a multiplication by a power of 5. The best way is to observe that 25 = 5². There are 2 powers of 5. So append 2 zeroes and divide by 2², like this: $53200/4$ = 13300.

Let them have X and Y marbles, respectively. We have X - 3 = Y + 3, which gives X - Y = 6. By the second condition, X + 4 = 2(Y - 4), which can be re-arranged to X - 2Y = -12. Solving for Y, we get Y = 18.

Let the duration be x days. We have $300/x$ - $300/{x + 5}$ = 10. This equation can now be solved, or you can try substituting the options one by one, to obtain x = 10 days.

This is a multiplication by a number that contains 9 only. Proceed like this: 335 × 9999 = 335 × (10000 - 1) = 335 × 10000 - 335 = 3350000 - 335 = 3349665.