Question
A container has 30 litres of a solution of milk and
water in which water is 20% by volume. How many litres of water must be added so that water becomes 30% of the final mixture?Solution
Initial total = 30 L Water initially = 20% of 30 = 6 L Milk = 24 L Let x litres of water be added. New total volume = 30 + x New water volume = 6 + x Required water % = 30%: (6 + x) / (30 + x) = 0.30 6 + x = 0.30(30 + x) 6 + x = 9 + 0.3x x − 0.3x = 9 − 6 0.7x = 3 x = 3 / 0.7 = 30/7 Answer: 30/7 litres of water must be added.
60, 100, 160, 240, ?, 460
What will come in place of the question mark (?) in the following series?
4, 36, 31, 279, 275, 2475, ?
Find the missing number in the given number series.
4, 9, 20, 37, 60, ?23, 39, 64, 100, ?, 213
8 12 30 105 ? 2598.75
...18, 30, 46, 66, 90, ?
142, 148, 160, 178, ?, 232
4, 7, 12, 21, 36, ?
24, 12, 18, 45, ?, 708.75
45, ?, 84, 114, 151, 195