Out of four numbers ,the average of first three is 16 and that of the last three is 15. If the last number is 21,the first number is : Choose the correct choice
A) 22
B) 21
C) 77
D) 99
E) 24
24xplanation:   Let the numbers be a,b,c,d   Given, a + b + c = 48, b + c + d = 45   Now, d = 21   thus, b + c + 21 = 45 ⇒ b + c = 24   Putting the value of b + c in a + b + c = 48   a + 24 = 48 ⇒ a = 24   Answer: 24
<result>E</result>
Out of four numbers ,the average of first three is 16 and that of the last three is 15. If the last number is 21,the first number is :