5. There was an equal number of boys and girls at an exhibition. After 3/5 of the boys and 42 girls had left the exhibition, there were 12 more boys than girls at the exhibition. How many pupils were there at the exhibition at first?


Can anyone help to how to explain to my kid where it is 3 units 42-12 = 30.

Thank you in advance

Gladys wrote:
5. There was an equal number of boys and girls at an exhibition. After 3/5 of the boys and 42 girls had left the exhibition, there were 12 more boys than girls at the exhibition. How many pupils were there at the exhibition at first?

Can anyone help to how to explain to my kid where it is 3 units 42-12 = 30.
Thank you in advance
While waiting for others to explain using model drawings, try solving this question using units.

Before
B: 5u
G: 5u
since there was an equal number of boys and girls at first.

Change
B: 3/5 of the boys left ie 3u of the boys left
G: 42 girls left

After
12 more boys than girls in the end

B: 5u-3u=2u
G: 5u-42

To balance up, 5u-42+12=2u
5u-2u=42-12
3u=30
u=10

At first, total number of boys+girls = 5u+5u=10u = 10x10=100
100 pupils were at the exhibition at first.

There was an equal number of boys and girls at an exhibition. After 3/5 of the boys and 42 girls had left the exhibition, there were 12 more boys than girls at the exhibition. How many pupils were there at the exhibition at first?

Can anyone help to how to explain to my kid where it is 3 units 42-12 = 30.

Perhaps this model drawing can help you. Notice that the shaded 3units of boys that left is the same as 42-12. This is depicted by the second red line.