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Q76·CSAT · Prelims 2023

Cryptarithm AB x CD = DEF, DEF + GHI = 975

ReasoningCryptarithmeticCoding-decodingHard

Question

AB and CD are 2-digit numbers. Multiplying AB with CD results in a 3-digit number DEF. Adding DEF to another 3-digit number GHI results in 975. Further A, B, C, D, E, F, G, H, I are distinct digits. If E = 0, F = 8 then what is A + B + C equal to ?

Options

a

6

Answer
b

7

c

8

d

9

Explanation

We are given that E = 0 and F = 8, so the product DEF = D08[cite: 4402, 4467]. Substitute this into the second cryptarithm addition equation: D08 + GHI = 975 [cite: 4400, 4466]

Evaluate the column addition from right to left:

Units place: 8 + I must end in 5 \implies 8 + I = 15 \implies I = 7 (carrying 1 to the tens column) .
Tens place: 0 + H + 1 (carry) = 7 \implies H = 6 .
Hundreds place: D + G = 9.

The digits used so far are \{0, 6, 7, 8\}. The remaining open digits are \{1, 2, 3, 4, 5, 9\}. Since D + G = 9, the only available pair from our remaining pool is (4, 5) or (5, 4). Thus, D can only be 4 or 5.

Now evaluate the multiplication: AB × CD = D08[cite: 4398, 4399, 4465].

If D = 5, AB × CD = 508. The prime factorization of 508 = 4 × 127. It has no 2-digit factor pairs.
If D = 4, AB × CD = 408. Let's test 2-digit factors of 408 using our remaining pool \{1, 2, 3, 4, 5\}: 12 × 34 = 408.

This configuration works perfectly and uses the distinct digits A=1, B=2, C=3, D=4, G=5, H=6, I=7, E=0, F=8. All 9 digits are completely distinct[cite: 4401, 4466]. Calculate the required sum: A + B + C = 1 + 2 + 3 = 6.

For multi-tier system cryptarithms, isolate the column parameters of the additive component first to uniquely lock the leading digits of the multiplicative component.

Answer: (a).

Question details

Year

2023

Paper

CSAT

Question

Q76

Section

Logical & Analytical Reasoning

Sub-topic

Cryptarithmetic

Type

Coding-decoding

Difficulty

Hard

Source hint

Cryptarithmetic puzzle

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