Question

This grid follows two rules.

Rule 1 The sums of each row are equal.
Rule 2 The products of each column are equal.
The grid below follows the same two rules.
Work out the missing numbers.
a =
b =
c =
d =

Answer 1

a = 4,

b = 12

c = 10

d = 15

Explanation:

Since the product of each column is equal, therefore,

b*5 = 60

b = 60 ÷ 5 = 12

c*6 = 60

c = 60 ÷ 6 = 10

Since the sum of each column are equal, therefore,

12 + 10 + a = 5 + 6 + d

22 + a = 11 + d

Think of a number you can add to 22, and another number you can add to 11, which will make both sides equal. Add both numbers, whenmultiplied together should give you 60.

Factors of 60 are:

(a, d)

(1, 60) => 22 + a = 11 + d => 22+1 = 11+60 (incorrect)

(2, 30) => 22 + a = 11 + d => 22+2 = 11+30 (incorrect)

(3, 20) => 22 + a = 11 + d => 22+3 = 21+20 (incorrect)

(4, 15) => 22 + a = 11 + d => 22+4 = 11+15 => 26 = 26 [CORRECT]

(5, 12) => 22 + a = 11 + d => 22+5 = 11+12 (incorrect)

(6, 10) => 22 + a = 11 + d => 22+6 = 11+10 (incorrect)

Therefore,

a = 4,

d = 15