Question : Directions: By Interchanging which two signs the equation will be correct?
21 – 7 × 4 ÷ 10 + 2 = 4
Option 1: – and ×
Option 2: × and ÷
Option 3: – and ÷
Option 4: + and –
Correct Answer: – and ÷
Solution :
Given:
21 – 7 × 4 ÷ 10 + 2 = 4
Replace the given symbols in the options one by one with the original symbols in the given equation.
First option:
– and ×
Solving the L.H.S. of the equation –
= 21 × 7 – 4 ÷ 10 + 2
= 147 – 0.4 + 2
= 148.6 ≠ 4
Second option:
× and ÷
Solving the L.H.S. of the equation –
= 21 – 7 ÷ 4 × 10 + 2
= 21 – 17.5 + 2
= 5.5 ≠ 4
Third option:
– and ÷
Solving the L.H.S. of the equation –
= 21 ÷ 7 × 4 – 10 + 2
= 12 – 10 + 2
= 4 = R.H.S.
Fourth option:
+ and –
Solving the L.H.S. of the equation –
= 21 + 7 × 4 ÷ 10 – 2
= 21 + 2.8 – 2
= 21.8 ≠ 4
So, only the third option satisfies the R.H.S. of the given equation. Hence, the third option is correct.
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