Question

7:

The mean of six numbers is 25.
​
​Three of the numbers are 15,15 and 30.
​
​The second unknown number is twice the first unknown number, and third unknown number is twice the sum of the first two unknown numbers.
​
​Find the unknown numbers.
​Select all that apply.
A
12
B
10
C
60
D
25
E
20
F
30
G
5

Answer 1

(B) (C) (E)

Explanation:

15, 15, 30 = 60

The 3 numbers sum is equal to 90

first number uknown = x

seconds unknown number = y

third unkown number = z

2x = y

2x + 2y = z

2x + 2(2x) = z

2x + 4x = z

6x = z

x + 2x + 6x = 90

9x = 90

× = 10

2× = y

20 = y

6x = y

60 = y

10, 20, 60