Select the correct combination of mathematical signs to sequentially place from left to right in the blanks below to balance the given equation. 8 _ 27 _ 9 _ 6 _ 5 = 0
- (a)−, ÷, +, +
- (b)÷, +, −, +
- (c)+, ÷, −, −
- (d)−, +, ÷, +
Answer
Why
Correct — C.
Rule: substitute each option into the blanks, then evaluate under BODMAS — division before addition and subtraction, whatever the printed order looks like.
Putting in +, ÷, −, − gives 8 + 27 ÷ 9 − 6 − 5.
Division first: 27 ÷ 9 = 3
8 + 3 − 6 − 5 = 11 − 11 = 0
The equation balances, so the combination is option (c).
Why the others are wrong
- (a)−, ÷, +, + — −, ÷, +, + gives 8 − 27 ÷ 9 + 6 + 5 = 8 − 3 + 6 + 5 = 16. The two plus signs at the tail push the total up, away from zero.
- (b)÷, +, −, + — ÷, +, −, + gives 8 ÷ 27 + 9 − 6 + 5. The opening division is not exact, and the total comes to about 8.30.
- (d)−, +, ÷, + — −, +, ÷, + gives 8 − 27 + 9 ÷ 6 + 5 = 8 − 27 + 1.5 + 5 = −12.5. Dividing 9 by 6 instead of 27 by 9 is the misstep.
Concept
Sign-substitution items are arithmetic rather than reasoning: four options are offered and testing them is the method. What decides the question is BODMAS, applied to the substituted line and not left to right.
A quick filter saves time. Two of the options divide 27 by 9, which is exact; the other two divide 8 by 27 and 9 by 6, which are not, and no later whole-number step clears a fraction here.
So start with an option whose division comes out exact, evaluate it in full, and stop the moment the line balances.
Key facts
- Under BODMAS, 8 + 27 ÷ 9 − 6 − 5 = 8 + 3 − 6 − 5 = 0.
- Signs are placed into the blanks from left to right, but evaluation still follows BODMAS.
- Of the divisions the four options create, only 27 ÷ 9 comes out whole.
Study next
Common traps
- Evaluating left to right and computing (8 + 27) ÷ 9 instead of 8 + (27 ÷ 9)
- Committing to an option before checking that its division comes out whole
The same place-the-signs-to-balance frame is set at 25 Sep 2024, 09:00, Reasoning Q.9. Its cousin, where two signs are interchanged instead of supplied, is at 19 Sep 2024, 12:30, Reasoning Q.11.
Related PYQs
No directly related past PYQ was found.