Basic Simplification Quiz Set 005

Let there be N coins of each denomination. Then N × (1 + 5 + 10) = 400, which gives N = $400/16$, and 3N = 3 × $400/16$ = 75.

Let the duration be x days. We have $180/x$ - $180/{x + 3}$ = 10. This equation can now be solved, or you can try substituting the options one by one, to obtain x = 6 days.

This is a multiplication by a number that contains 9 only. Proceed like this: 224 × 99 = 224 × (100 - 1) = 224 × 100 - 224 = 22400 - 224 = 22176.

Had he attempted all correctly, he would have got 150 × 4 = 600. But he has lost 600 - 195 = 405 marks due to wrong attempts. Each wrong attempt leads to an overall loss of 5 marks, so the number of wrong attempts is 405/5 = 81.

This is a multiplication by a number whose units place is 9. Proceed like this: 465 × 69 = 465 × (60 + 9) = 465 × (60 + 10 - 1) = (465 × 60) + (465 × 10) - 465 = 27900 + 4650 - 465 = 32085. The other approach could have been 465 × 69 = 465 × (70 - 1), etc.,