What will come in place of the question mark (?) in the following equation, if ‘+’ and ‘–’ are interchanged and ‘×’ and ‘÷’ are interchanged? 321 – 371 ÷ 22 + 216 × 6 = ?

Correct — D. Rule: swap the symbols first, then apply BODMAS to the rewritten line.

Given: 321 - 371 ÷ 22 + 216 × 6
After swapping + with - and × with ÷: 321 + 371 × 22 - 216 ÷ 6

Multiplication and division first.
371 × 22 = 8162
216 ÷ 6 = 36

Then addition and subtraction, left to right.
321 + 8162 = 8483
8483 - 36 = 8447, option (d).

Why the others are wrong

• (a)
  7848 — After the swap, 371 × 22 = 8162 is an added term and only 36 is ever taken away, so the total cannot drop below 8126. 7848 sits under that floor.
• (b)
  7884 — The last digit settles it. The rewritten line finishes + 8162 - 36, so the total must end in 7, and 7884 ends in 4.
• (c)
  8747 — 8747 clears both quick checks, so it has to be settled by arithmetic: 321 + 8162 = 8483 and 8483 - 36 = 8447. 8747 is 300 too large.

A symbol-interchange item tests two things in sequence, and candidates lose it on the second.

Step one is clerical: rewrite the expression with the new symbols in place. Step two is ordinary BODMAS on that rewritten line, with division and multiplication settled before addition and subtraction.

Do not try to hold the swap in your head while evaluating. Writing the swapped line out costs four seconds and removes the only real source of error.

Key facts

• After the swap the expression reads 321 + 371 × 22 - 216 ÷ 6.
• 371 × 22 = 8162.
• 216 ÷ 6 = 36.
• The value of the swapped expression is 8447.

Common traps

• Swapping only one of the two pairs and leaving the other as printed.
• Evaluating left to right after the swap instead of doing × and ÷ first.

No directly related past PYQ was found.