Question : Directions: Which two signs should be interchanged, to make the given equation correct?
2 ÷ 9 × 18 + 7 – 4 = 1
Option 1: = and ×
Option 2: = and –
Option 3: – and +
Option 4: × and +
Correct Answer: – and +
Solution :
Given:
2 ÷ 9 × 18 + 7 – 4 = 1
Replace the given symbols in the options one by one with the original symbols in the given equation.
First option:
= and ×
2 ÷ 9 × 18 + 7 – 4 = 1
On interchanging the mathematical signs, we get –
2 ÷ 9 = 18 + 7 – 4 × 1
L.H.S. = 2 ÷ 9 = 0.22
R.H.S. = 18 + 7 – 4 × 1
= 18 + 7 – 4
= 18 + 7 – 4
= 0.22 ≠ 21
Second option:
= and –
2 ÷ 9 × 18 + 7 – 4 = 1
On interchanging the mathematical signs, we get –
2 ÷ 9 × 18 + 7 = 4 – 1
L.H.S. = 2 ÷ 9 × 18 + 7
= 4 + 7 = 11
R.H.S. = 4 – 1 = 3
= 11 ≠ 3
Third option:
– and +
2 ÷ 9 × 18 + 7 – 4 = 1
On interchanging the mathematical signs, we get –
2 ÷ 9 × 18 – 7 + 4 = 1
L.H.S. = 2 ÷ 9 × 18 – 7 + 4
= 4 – 7 + 4
= 1
Fourth option:
× and +
2 ÷ 9 × 18 + 7 – 4 = 1
On interchanging the mathematical signs, we get –
2 ÷ 9 + 18 × 7 – 4 = 1
L.H.S. = 2 ÷ 9 + 18 × 7 – 4
= 0.22 + 18 × 7 – 4
= 0.22 + 126 – 4
= 122.22
= 122.22 ≠ 1
Here, only the third option satisfies the R.H.S. of the given equation. Hence, the third option is correct.
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