Question

1+2=21; 2+3=36; 3+4=43; 4+5=

Answer 1

The required number is "90".

Step-by-step explanation:

We have,

1 + 2 = 21;  2 + 3 = 36; 3 + 4 = 43

To find 4 + 5 = ?

1 + 2 = $(1 + 2)^{2}$ + 12 = 9 + 12 = 21,

2 + 3 = $(2 + 3)^{2}$ + 11 = 25 + 11 = 36

3 + 4 = $(3 + 4)^{2}$ + 10 = 49 + 10 = 59

∴ Missing number (?) = 3 + 4 = $(4 + 5)^{2}$ + 9 = 81 + 9 = 90

Hence, the required number is "90".