1. Average age of A, B and C is 84 years. When D joins them the average age becomes 80 years. A new person, E, whose age is 4 years more than D, replaces A and the average of B, C, D and E becomes 78 years. What is the age of A ?
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By: anil on 05 May 2019 01.53 am
avg age of a,b,c = 84 $$frac{A+B+C}{3}$$ = 84
A+B+C = 84*3 =252 ........................(1) similarly , $$frac{A+B+C+D}{4}$$ = 80 A+B+C+D = 80*4 = 320 so using (1) 252 + D = 320 D = 68 i.e, E = 72 (as mentioned in the question)................(2) $$frac{B+C+D+E}{4}$$ = 78 B+C+D+E = 78*4 = 312 using (2) B+C+68+72 =312 B+C = 172 .................................(3) put (3) in (1) A = 80
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A+B+C = 84*3 =252 ........................(1) similarly , $$frac{A+B+C+D}{4}$$ = 80 A+B+C+D = 80*4 = 320 so using (1) 252 + D = 320 D = 68 i.e, E = 72 (as mentioned in the question)................(2) $$frac{B+C+D+E}{4}$$ = 78 B+C+D+E = 78*4 = 312 using (2) B+C+68+72 =312 B+C = 172 .................................(3) put (3) in (1) A = 80