Question : Directions: Which two mathematical signs should be interchanged to make the given equation correct?
(63 × 21) + 8 + 99 × 11 ÷ 16 + (12 × 4) = 158
Option 1: + and –
Option 2: × and +
Option 3: × and –
Option 4: ÷ and ×
Correct Answer: ÷ and ×
Solution :
Given:
(63 × 21) + 8 + 99 × 11 ÷ 16 + (12 × 4) = 158
Interchange the symbols according to the given options to make the equation correct.
Let's check the options –
First option:
+ and –
⇒ (63 × 21) – 8 – 99 × 11 ÷ 16 – (12 × 4) = 158
(1323) – 8 – 99 × 11 ÷ 16 – (48) = 158
1323 – 8 – 99 × 0.68 – 48 = 158
1323 – 8 – 67.32 – 48 = 158
1199.68 ≠ 158
Second option:
× and +
⇒ (63 + 21) × 8 × 99 + 11 ÷ 16 × (12 + 4) = 158
84 × 8 × 99 + 11 ÷ 16 × 16 = 158
84 × 8 × 99 + 0.6875 × 16 = 158
84 × 8 × 99 + 0.6875 × 16 = 158
66528 + 10.88 = 158
66538.88 ≠ 158
Third option:
× and –
⇒(63 – 21) + 8 + 99 – 11 ÷ 16 + (12 – 4) = 158
42 + 8 + 99 – 11 ÷ 16 + 8 = 158
42 + 8 + 99 – 0.68 + 8 = 158
156.32 ≠ 158
Fourth option:
÷ and ×
⇒(63 ÷ 21) + 8 + 99 ÷ 11 × 16 + (12 ÷ 4) = 158
3 + 8 + 9 × 16 + 3 = 158
3 + 8 + 144 + 3 = 158
158 = 158
So, only the fourth option satisfies the given equation. Hence, the fourth option is correct.
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