Question : Directions: Which two signs should be interchanged to make the given equation correct?
551 ÷ 19 – 16 × 12 + 121 = 100
Option 1: – and ×
Option 2: + and ×
Option 3: ÷ and ×
Option 4: + and –
Correct Answer: + and –
Solution :
Given:
551 ÷ 19 – 16 × 12 + 121 = 100
Let's check the options –
First option:
– and ×
On interchanging the mathematical signs, we get –
= 551 ÷ 19 × 16 – 12 + 121
= 29 × 16 – 12 + 121
= 464 – 12 + 121
= 585 – 12
= 573
≠ 100
Second option:
+ and ×
On interchanging the mathematical signs, we get –
= 551 ÷ 19 – 16 + 12 × 121
= 29 – 16 + 12 × 121
= 29 – 16 + 1452
= 1481 – 16
= 1465
≠ 100
Third option:
÷ and ×
On interchanging the mathematical signs, we get –
= 551 × 19 – 16 ÷ 12 + 121
= 551 × 19 – 1.33 + 121
= 10469 – 1.33 + 121
= 10590 – 1.33
= 10588.67
≠ 100
Fourth option:
+ and –
On interchanging the mathematical signs, we get –
= 551 ÷ 19 + 16 × 12 – 121
= 29 + 16 × 12 – 121
= 29 + 192 – 121
= 221 – 121
= 100
Only the fourth option satisfies the given equation. Hence, the fourth option is correct.
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