Question
How much water is to be added to 75 ml of alcohol, so
that the mixture contains 20% of alcohol?Solution
ATQ,
Pure alcohol = 75 ml Final solution should be 25% alcohol Need to find: How much water to add Let water added = x ml So, total solution = 75 + x ml We want alcohol to be 25% of the total solution: 
On Solving the equation: 
What will come in place of the question mark (?) in the following series?
1528, 1416, 1204, ?, 480, -32
143 Â Â Â Â 119Â Â Â Â 107Â Â Â Â 101Â Â Â Â Â 98Â Â Â Â ?
96 89 ? 90 94 91
...What value should come in the place of (?) in the following number series?
19, 235, 260, 324, 333, ?
What will come in place of the question mark (?) in the following series?
305...
In each of the following number series, one term is missing. Find the missing term.
3, 5, 20, 24, 144, 150, ?
1029, 1030, 1039, 1064, ?, 1194
75, 80, 95, ?, 155, 200
What will come in place of the question mark (?) in the following series?
1515, 184, ?, 455, 967, 624
7 29 61 ? 211 349
...
