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Numerical Ability
Averages
In seven given numbers, the average of first four numbers is 4 and that of the last four numbers is also 4. If the average of these seven numbers is 3, the fourth number is :
a. 3
b. 4
c. 7
d. 11
Read Solution (Total 1)
-
- let the no.s be;
X1,X2,X3,X4,X5,X6,X7
X1+X2+X3+X4 divided by 4=4
there for;X1+X2+X3+X4=16 (cross multiply)
just like that
X4+X5+X6+X7=16
there for;
X1+X2+X3+X4 = X4+X5+X6+X7
X1+X2+X3 = X5+X6+X7 (X4 is common so it is cancelled)
X1+X2+X3+X4+X5+X6+X7 divided by 7 =3 (given in the question)
this can be written as;
(16 - X4) + X4 +( 16 - X4)=21 (cross multiply to get 21)
-X4 = 21-32
-X4 = -11
SO,
X4 = 11 . 4TH NO. IS 11. - 11 years agoHelpfull: Yes(4) No(0)
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