Given below is an equation which has to be solved by following the interchange i.e., + becomes − and − becomes + × becomes ÷ and ÷ becomes × Then what is the value of 100 ÷ 5 + 20 − 10 × 2 = ?

Correct — D.
Rule: swap + with − and × with ÷, then apply BODMAS.

100 ÷ 5 + 20 − 10 × 2 becomes 100 × 5 − 20 + 10 ÷ 2
100 × 5 = 500 and 10 ÷ 2 = 5
500 − 20 + 5 = 485 → option (d).

Why the others are wrong

• (a)
  534 — 534 overshoots. After the swap, 500 is the biggest term, and − 20 + 5 takes it down to 485, not up.
• (b)
  330 — 330 is far below the swapped value. 100 × 5 alone is 500, and the rest of the expression changes it by only 15.
• (c)
  22 — 22 is far too small. Once ÷ becomes ×, the first term alone is 100 × 5 = 500.

An interchange item hands you a substitution table: every printed + is really −, every printed − is really +, and × and ÷ swap the same way.

Rewrite the whole expression first, sign by sign. Only then apply BODMAS: here the two products, 100 × 5 and 10 ÷ 2, are worked before any adding or subtracting.

Key facts

• After the swap the expression is 100 × 5 − 20 + 10 ÷ 2 = 485.
• Without the swap, 100 ÷ 5 + 20 − 10 × 2 is 20 + 20 − 20 = 20, which is not among the options.

Common traps

• Working the swapped expression left to right: 500 − 20 + 10 = 490, then ÷ 2 = 245.
• Swapping + and − but forgetting × and ÷, which gives 20 − 20 + 20 = 20.

No directly related past PYQ was found.