Paper 1 · Mathematical Reasoning and Aptitude
UGC NET December 2022 (03.03.2023) Shift-II
The average age of a family of six members is 30 years. The youngest members of the family are twins aged 10 years. Find the average age of the family just before the birth of the twins.
A28 years
B25 years
C30 years ✓ Correct
D32 years
Correct answer: (C) 30 years — The average age just before the birth of the twins is 30 years, so the answer is 30 years.
Explanation
★The average age just before the birth of the twins is 30 years, so the answer is 30 years.
★The six members have an average age of 30, so their ages sum to 180 years.
★The twins are each 10 years old, together 20 years.
★Ten years ago, just before their birth, each of these ages was 10 years less.
★The other four members were each 10 years younger, which is 40 years less in all.
★So the sum then was 180 minus 20 minus 40, which is 120, over four members, giving 30.
★So the answer is 30 years.
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