DAY 21

Comment

We are told that 21 lots of 31 are 651.
So, 22 lots of 31 will be 651 + 31, which is 682.
So, 22 lots of 32 will be ... .

Answer

22 x 32 = 704.

Readers' methods

Kent Swift, EX16 9JW:
The diagram shows that 22 x 32 = 651 + 21 + 31 + 1 = 651 + 53 = 704.

Adrian Thacker, Loughborough
(also JM, Milton Keynes, MK7; Hugh B, Riseley MK44):
A simple arithmetic approach would be
21 x 31 = 651
so 22 x 31 = 651 + 31 = 682
so 22 x 32 = 682 + 22 = 704.

Adrian Thacker, Loughborough
(also Ray Hobby, Northampton):
A more mathematical approach would be
22 x 32 = (21 + 1)(31 + 1)
= (21 x 31) + (1 x 31) + (21 x 1) + (1 x 1)
= 651 + 31 + 21 + 1
= 704.

G Mawson, EN3:
(a + 1)(b + 1) = ab + a + b + 1
so 22 x 32 = 651 + 21 + 31 + 1
= 704.