Speed = Distance/Time If the time is to be reduced 20% then the same distance is to be covered in 80% of the time. Therefore Speed = 100/80x100?125% of the original speed. The increase in the speed must be 25%.

Solve the question using only boys. The ration 7/29 = x/21+8. The second ration is reverse as the relation between men (or boys) is inverse. If 4 men work equivalent to 7 boys so 12 men are equivalent to 21 boys.

x is the amount in the start. After spending 10% the rest is 90x/100. Now treat this remaining amount as 100% for the second transaction. After spending 60% the rest is 40% of 90x/100 that is 40/100 90x/100 = 36x/100. Now this is equal to 72. 36x/100 = 72 ? x = 200

The average (arithmetic mean) of five numbers is 26. After one of the numbers is removed the average (arithmetic mean) of the remaining number is 25. What number has been removed?

x is the number to be removed and n is the sum of other 4 numbers. Therefore x+n/5 = 26?x + n = 130. Now by removing the number n/4 = 25 ? n = 100. Now put the value of n in the first x +100 = 130 and x = 30