Question

If 2 + 3 = 8
3 + 7 = 27
4 + 5 = 32
5 + 8 = 60
8 + 7 = 72
then 7 + 8 = ??

Which number replace the question mark​

Answer 1

Answer:

98

Step-by-step explanation:

Used rule: A × B + A (A - 1)

Apply the above rule on first case 1) i.e. 2 + 3 = 8. Here 2 is A and 3 is B. So,

→ 2 × 3 + 2(2 - 1) = 6 + 2(1) = 6 + 2 = 8

Similarly apply the same rule on rest cases.

→ 3 × 7 + 3(3 - 1) = 21 + 3(2) = 21 + 6 = 27

→ 4 × 5 + 4(4 - 1) = 20 + 4(3) = 20 + 12 = 32

→ 5 × 8 + 5(5 - 1) = 40 + 5(4) = 40 + 20 = 60

In question it's written that 8 + 7 = 72 but in actual it is 6 + 7 = 72. How I came to know that? If you look carefully then you will notice that starting digit's are a part of consecutive counting.

Therefore,

→ 6 × 7 + 6(6 - 1) = 42 + 6(5) = 42 + 30 = 72

Hence,

→ 7 × 8 + 7(7 - 1) = 56 + 7(6) = 56 + 42 = 98

The number which replace the question mark is 98.