Question

A glass is

4
7
full. Then 70cm3 of orange juice is poured in.
The glass is now
3
4
full. What is the total volume of the glass?

Answer 1

• 392 cm³

Explanation:

The difference of 3/4 and 4/7 of the volume is 70 cm:

• 3/4 - 4/7 = 7/7*3/4 - 4/4*4/7 = 21/28 - 16/28 = 5/28

5/28 of the volume is 70 cm³

Divide both numbers by 5/28 to find the total volume of the glass:

• 70 : 5/28 = 70*28/5 = 392 cm³

Answer 2

Explanation:

4/7 x + 70 cm^3 = 3/4 x Subtract 4/7 x from both sides

3/4 x - 4/7 x = 70 cm^3 The lowest common denominator is 28

`(3*7*x)/(4*7) - (4*4x)/(4*7) = 70 cc\\(21*x)/(28) - (16*x)/(28) = 70 cc\\(5x)/(28)= 70cc\\`

5x = 70*28

5x = 1960 Divide by 5

x = 1960/5

x = 392 cc