SSC CGL 2025 Tier-I · 15 September 2025, Shift 2 · General Intelligence and Reasoning · Question 21 of 100

We transcribed this text from the pictures on a candidate's response sheet for this shift; the answer is the key SSC colour-marked on that sheet. Solution last reviewed 11 September 2026.

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If 5 * 2 = 35, 4 * 3 = 28, then what is 6 * 4?

(a)42
(b)48
(c)54
(d)60

Answer

Why

Correct — D.
Rule: a * b = a × (a + b).

5 * 2 = 5 × (5 + 2) = 5 × 7 = 35, as given
4 * 3 = 4 × (4 + 3) = 4 × 7 = 28, as given
6 * 4 = 6 × (6 + 4) = 6 × 10 = 60 → option (d).

Why the others are wrong

(a)
42 — 42 is 6 × 7, keeping the 7 from the examples. That 7 was 5 + 2 and 4 + 3; for 6 * 4 the sum is 6 + 4 = 10.
(b)
48 — 48 is 6 × 8, and 8 is not 6 + 4. Doubling the product, 2 × 6 × 4, also gives 48 but fails the examples: 2 × 5 × 2 = 20, not 35.
(c)
54 — 54 is 6 × 9, one short of the right multiplier. The rule multiplies 6 by 6 + 4 = 10.

Concept

A made-up operator hides a rule built from its two numbers. Test a candidate rule on every example before trusting it.

Here 35 = 5 × 7 and 28 = 4 × 7. The 7 is not fixed: it is 5 + 2 in one example and 4 + 3 in the other. So the rule multiplies the first number by the sum, a × (a + b), which is the same as a² + ab.

Both examples add to 7, so 'first number × 7' also reproduces 35 and 28, and would give 42. That reading never uses the second number, so it is not really a rule for a * b. The key takes a × (a + b), which uses both.

Key facts

a × (a + b) = a² + ab: 5² + 5 × 2 = 25 + 10 = 35.
A rule must reproduce every example given, not just the first.
A number the examples share, like the 7 here, may be built from the operands rather than fixed.

Study next

Operators defined as a² + b or (a + b) × bOdd-one-out among equations that share a hidden ruleNumber analogies built on squares and cubes

Common traps

Reading 7 as a fixed multiplier and choosing 42
Stopping after the first example, where several rules give 35

14 Sep 2025, 12:30, Reasoning Q.15 uses the mirror rule (a + b) × b: 9 @ 3 = 12 × 3 = 36, and 8 @ 2 is keyed 20.

18 Sep 2025, 12:30, Reasoning Q.21 looks similar, but a × (a + b) fails there because 5 @ 5 would be 50, not 100; (a + b) × 10 fits both examples and gives the keyed 110.

Related PYQs

No directly related past PYQ was found.

Topic: Symbolic/Number Analogy — all 169 SSC CGL questions on it, every solved shift.