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Suraj Kumar Singh

· started a discussion

· 1 Months ago

Answer is wrong (Question: 86227.0 )

It should be (144+36)/2=90

Question:
Among three number, the first number is thrice the second number and one-fourth of the third number. The average of all three numbers is 64. What is the average of first and third number? 
Options:
A) 30 
B) 24 
C) 90
D) 78
E) 88
Solution:

Ans: (c)Suppose third number = x

∴ First number =  \(\cfrac{x}{4}\)

∴ Second number =  \(\cfrac{x}{12}\)

Then, x+\(\cfrac{x}{4}+\cfrac{x}{12}\) = 3 × 64

⇒  \(\cfrac{12x+13x+x}{12}\)= 3 × 64

⇒ \(\cfrac{16x}{12}\) = 3 × 64

⇒ x =  \(\cfrac{12\times3\times64}{16}\)

⇒ x = 144

Hence, required average =   \(\cfrac{144+36}{2}\)

=  \(\cfrac{180}{2}\)

= 90

kanhaiya jha

· commented

· 1 Months ago

option(c) is correct........
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