If 8 × 5 means 8 – 52 and 9 $ 3 means √9 + 32, then what is the value of 25 ×…
2016
If 8 × 5 means 8 – 52 and 9 $ 3 means √9 + 32, then what is the value of 25 × 3 $ 6?
- A.
34
- B.
36
- C.
52
- D.
40
Attempted by 24 students.
Show answer & explanation
Correct answer: D
Concept: In symbol-substitution (operator-renaming) reasoning questions, an unfamiliar sign such as '×' or '$' is redefined by a worked example. Read the example as a general rule linking the two numbers involved, then apply that same rule — with the actual numbers from the question — strictly in the order the expression is written.
Application:
From '8 × 5 means 8 – 52', the rule for '×' is: p × q = p – q2.
From '9 $ 3 means √9 + 32', the rule for '$' is: r $ s = √r + s2.
Apply '×' first: 25 × 3 = 25 – 32 = 25 – 9 = 16.
Apply '$' to that result and 6: 16 $ 6 = √16 + 62 = 4 + 36 = 40.
Cross-check: 32 = 9 and 25 – 9 = 16 is a perfect square, so √16 is exactly 4; adding 62 = 36 gives 4 + 36 = 40, with no fractional or negative value appearing at any step — confirming the substitutions were applied correctly and in the right order.
The value of 25 × 3 $ 6 is 40.