There are four persons A, B, C, D; and A has some coins. A gave half of the coins to B and 4 more besides. B gave half of the coins to C and 4 more besides. C gave half of the coins to D and 4 more besides. Both B and D end up with same number of coins. How many coins did A have originally?
Reviewed by Dalvoy
UPSC Civil Services preparation
- A96
- B84
- C72Correct
- D64
Explanation
To solve this problem, we work backward or use the options to verify. Let the original number of coins with A be x.
Step 1: A gives half and 4 more to B.
A gives x/2 + 4 to B.
A is left with x/2 - 4.
Step 2: B gives half of what he received and 4 more to C.
B received x/2 + 4.
B gives away (x/2 + 4)/2 + 4 to C.
B is left with (x/2 + 4)/2 - 4.
Simplifying B's remaining coins: x/4 + 2 - 4 = x/4 - 2.
Step 3: C gives half of what he received and 4 more to D.
C received (x/4 + 2 + 4) = x/4 + 6.
D receives (x/4 + 6)/2 + 4.
Simplifying D's coins: x/8 + 3 + 4 = x/8 + 7.
Step 4: Set B's remaining coins equal to D's coins.
x/4 - 2 = x/8 + 7.
Multiply the entire equation by 8 to clear denominators:
2x - 16 = x + 56.
x = 72.
If we check with 72:
A has 72.
A gives 36 + 4 = 40 to B.
B has 40. B gives 20 + 4 = 24 to C.
B is left with 40 - 24 = 16.
C has 24. C gives 12 + 4 = 16 to D.
D ends up with 16.
Since B and D both have 16, the answer is 72.

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