Question

Which two numbers should be interchanged to make the given equation correct?

9 × (34 - 15) + (105 ÷ 7) + 28 + (13 × 4) = 218

(Note: Interchange should be done of entire number and not individual digits of a given number)

• A. 28 and 15
• B. 15 and 13
• C. 34 and 28
• D. 15 and 7

Answer 1

Answer:

C. 34 and 28

First solve the original equation:

$9 × (34 - 15) + (105 ÷ 7) + 28 + (13 × 4)$

Step-by-step:

34 − 15 = 19
9 × 19 = 171
105 ÷ 7 = 15
13 × 4 = 52

Total:

171 + 15 + 28 + 52 = 266

But we need 218, which is 48 less than 266.

Now try interchanging entire numbers.

Interchange 34 and 28

New equation:

$9 × (28 - 15) + (105 ÷ 7) + 34 + (13 × 4)$

Now calculate:

28 − 15 = 13
9 × 13 = 117
105 ÷ 7 = 15
13 × 4 = 52

Total:

117 + 15 + 34 + 52 = 218

Equation becomes correct.

34 and 28 should be interchanged.