Sawaal
12
Q:

If 3a=4b=6c and a+b+c=2729, then a2+b2+c2 =?

A) 81 B) 83
C) 87 D) None of these

Answer:   C) 87



Explanation:

4b=6c⇒b=32c    and   3a=4b⇒a=43b=43(32c)=2c 

a+b+c=2729   ⇒2c+32c+c=2729  ⇒c=629

 

 ∴a2+b2+c2=(a+b+b)2-2(ab+bc+ca) 

 

=(2729)2-22c×32c+32c×c+c×2c 

 

 =729×29-2×132 c2

= 87

Subject: Square Roots and Cube Roots
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