at 12pm there are 855 people in the zoo by 5pm 4/5 of the children have left and ³/₄ of the adults have left. There are now 36 more children than adults in the zoo. working out

300 Adults 555 Children

Step-by-step explanation:

What we know:

Firstly, at 5pm there were 36 more Children (C) than Adults (A)

So ... C = A + 36

Secondly, at 12pm there were 5 x more Children and 4 x more Adults and the total was 855

So 4A + 5C = 855

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Now use 'C = A + 36' and get rid of all 'C' in the second equation ...

4A + 5C = 855

becomes ...

4A + 5 (A + 36) = 855

Multiply the brackets (5 x A) and (5 x 36):

4A + 5A + 180 = 855

Take off 180 from both sides:

4A + 5A = 675

Therefore 9A = 675

Divide by 9:

A = 75

We know C is A + 36

C = 111

At 5 pm - A = 75 and C = 111

Therefore at 12:

There were 5 x C = 555

And 4 x A = 300