Find the missing number from the given alternatives.
| 6 | 10 | 14 |
| 9 | 15 | 21 |
| 12 | 20 | ? |
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 28
In a number grid, the rule is looked for along the rows and down the columns, and the rule that fits every complete row is used for the incomplete one. Here each row is 3, 5 and 7 multiplied by one number: 2 in the first row, 3 in the second and 4 in the third.
Row 1: 6, 10, 14 \(=2\times3,\ 2\times5,\ 2\times7\)
Row 2: 9, 15, 21 \(=3\times3,\ 3\times5,\ 3\times7\)
Row 3: 12, 20, ? \(=4\times3,\ 4\times5,\ 4\times7\)
So the missing number is \(4\times7=28\).
The columns confirm it: the third column goes 14, 21, ?, rising by 7 each time like the multiples of 7, so the next number is \(21+7=28\).