Friday, February 27

Any Comments?

Dear Mr Sunny Tan,

1/5 of the children at the playground were girls and the rest were boys. When 8 girls left the playground, the fraction of girls decreased to 1/7 of the total number of children at the playground. How many children were at the playground at first? (Ans 120)


For the above Question in the UTM book (Pg 20),

We get the answer is 140 children.

Following is the detail

1/5 are girls and 4/5 are boys = 7/35 are girls and 28/35 are boys

8 girls left , so left 1/7 are girls and 6/7 are boys

1/7 will be equal to 5/35 are girls left.

so 7/35 minus 5/35 = 8 girls left

2 units = 8 girls

1 unit = 4

4 x 35 = 140

Check back the answer as follow

and 28-8 = 20 girls left in the playground.

20/140 = 1/7.

Please check.

Question Posted by Mdm Chong - UTM reader

1 comments:

Anonymous said...

120 is the right answer.

At first
Girls: Boys 1:4
In the end
Girls: Boys 1:6
Number of boys remains the same
Therefore
Girls: Boys 3:12
In the end
Girls: Boys 2:12
1 unit = 8 girls
Number of children = 15x8=120, at first

sheng tian



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