Question

3. The ratio of the number of students in three classes A,
B, and C'is 3:7:8. If ten students, are transferred from C
to B, B will have 80 students. Find the total number of
students in the three classes.
(A) 150 (B) 160 (180
(D) 210​

Answer 1

Answer:

A:B:C = 3:7:8

A:B+10:C-10 = 3:8:7

That means that

b/c = 7/8

(b+10)/(c-10) = 8/7

Solving that, we have

b=70

c=80

Now, you can figure a.

Answer 2

A:B:C = 3:7:8
Let A be 3x, B be 7x and C be 8x
If 10 students added to B from C, Number of students in B is 80
So,
=> B + 10 = 80
=> B = 80 - 10
=> B = 70
According to question,
=> B = 7x = 70
=> 7x = 70
=> x = 70/7
=> x = 10

So for A
=> 3x = 3× 10
=> 3x = 30

For C
=> 8x = 8× 10
=> 8x = 80

So, total sum= A+B+C
= 30+70+80
= 180
Ans = (C) 180