Question

Which two numbers should be interchanged to make the given equation correct? (24 + 14- 6) ÷ 2 + 18 × 3 - 20 = 40 (Note: Interchange should be done of entire number and not individual digits of a given number)

• A. 20 and 14
• B. 2 and 3
• C. 20 and 24
• D. 14 and 18

Answer 1

Answer:

D. 14 and 18

Let’s check the equation:

$(24 + 14 - 6) \div 2 + 18 \times 3 - 20 = 40$
Solve LHS normally

Inside bracket:
24 + 14 − 6 = 32

Now:
32 ÷ 2 + 18 × 3 − 20

= 16 + 54 − 20
= 50

But RHS = 40 (not correct)

Try interchanging numbers

We need the result to become 40, so reduce LHS by 10.

Try swapping 6 and 20

New equation:
$(24 + 14 - 20) \div 2 + 18 \times 3 - 6$

Solve again

Inside bracket:
24 + 14 − 20 = 18

Now:
18 ÷ 2 + 18 × 3 − 6

= 9 + 54 − 6
= 57

Try swapping 14 and 18

$(24 + 18 - 6) \div 2 + 14 \times 3 - 20$

Inside bracket:
24 + 18 − 6 = 36

Now:
36 ÷ 2 + 14 × 3 − 20

= 18 + 42 − 20
= 40

14 and 18 should be interchanged