Simplify the following:

- (a)

- (b)

- (c)

- (d)

Answer
Why
Correct — A. The stem is an image: [ (5½ − 3⅓) of 1 5⁄13 + 1 − 2 × 3 5⁄2 ÷ 2¾ ].
Bracket first, then 'of', then × and ÷ left to right, then + and −.
5½ − 3⅓ = 11⁄2 − 10⁄3 = 13⁄6
13⁄6 of 1 5⁄13 = 13⁄6 × 18⁄13 = 3
Now the ×÷ chain:
2 × 3 5⁄2 = 2 × 11⁄2 = 11
11 ÷ 2¾ = 11 × 4⁄11 = 4
3 + 1 − 4 = 0 → option (a)
Why the others are wrong
- (b)3½ would need the tail 2 × 3 5⁄2 ÷ 2¾ to be worth ½. It is worth 4, because 2 × 11⁄2 = 11 and 11 ÷ 11⁄4 = 4.
- (c)−2 would need the tail to be worth 6. The tail closes at 4, so the expression can fall no further than 3 + 1 − 4 = 0.
- (d)11⁄2 is the improper form of the mixed number 3 5⁄2 — a value picked up in the middle of the working, before the × 2 and the ÷ 2¾ are applied.
Concept
BODMAS fixes the order: brackets, then 'of', then division and multiplication together, then addition and subtraction together, each pair left to right.
'Of' behaves like a multiplication that has already been bracketed. SSC uses it precisely because a candidate who lets it wait its turn in the ÷× sweep gets a different number.
Convert every mixed number before you start: 5½ = 11⁄2, 3⅓ = 10⁄3, 1 5⁄13 = 18⁄13, 2¾ = 11⁄4.
The paper prints the fourth mixed number as 3 5⁄2 — a whole number beside an improper fraction, which looks like a typo but is not fatal.
Read it the way any mixed number is read, 3 + 5⁄2 = 11⁄2, and the chain closes on 0, the keyed value.
Key facts
- 'Of' is settled before ÷ and ×, so 13⁄6 of 18⁄13 is evaluated as one quantity, 3.
- Division and multiplication rank equally and run left to right: 2 × 11⁄2 ÷ 11⁄4 = 11 ÷ 11⁄4 = 4.
- Dividing by a fraction is multiplying by its reciprocal: 11 ÷ 11⁄4 = 11 × 4⁄11 = 4.
Study next
Common traps
- Treating 'of' as an ordinary × and letting it wait its turn in the left-to-right sweep
- Reading 3 5⁄2 as 3½ because the printed fraction looks improper
- Applying the minus sign before the ÷, so the tail is subtracted before it is evaluated
SSC prints the whole expression as a picture, so the bracket structure has to be read off the image before any arithmetic starts.
Simplification with 'of' is also asked at 13 Sep 2024, 09:00, Quant Q.15 and at 26 Sep 2024, 12:30, Quant Q.19.
Related PYQs
No directly related past PYQ was found.