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primary 5 | Maths
| Whole Numbers
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Date Posted: 3 years ago
Views: 635
a)
4 boys have total 700cm height.
Average = 700cm ÷ 4 = 175cm
b)
After they joined, average height for all becomes 163cm.
For the 4 boys, 163cm x 4 = 652cm
So some of the boys height has been averaged out i.e 'distributed' or 'split' among the girls.
700cm - 652cm = 48cm
48cm has been 'split' among the girls. The girls 'gained' 48cm in total.
The girls have average height of 157cm (within themselves only)
Since the new average is 163cm now,
163cm - 157cm = 6cm
Each girl 'gained' 6cm.
48cm ÷ 6cm per girl
= 6 girls
There were 6 girls in the first place.
4 boys have total 700cm height.
Average = 700cm ÷ 4 = 175cm
b)
After they joined, average height for all becomes 163cm.
For the 4 boys, 163cm x 4 = 652cm
So some of the boys height has been averaged out i.e 'distributed' or 'split' among the girls.
700cm - 652cm = 48cm
48cm has been 'split' among the girls. The girls 'gained' 48cm in total.
The girls have average height of 157cm (within themselves only)
Since the new average is 163cm now,
163cm - 157cm = 6cm
Each girl 'gained' 6cm.
48cm ÷ 6cm per girl
= 6 girls
There were 6 girls in the first place.
8 girls*
See 1 Answer
A) since total height of 4 boys is given as 700cm,
Average height of boys = 700cm/4 = 175cm
B) given the”new “ average height now after boys are added = 163cm
Difference in the average height of boy now is
= 175cm -163cm = 12cm decrease
Difference in an avg ht of a girl now
= 163cm -157cm =6cm
12 / 6= 2
Since the average height of boys is “decreased” this tells us there has to be more girls than boys. Therefore number of girls = 4x 2 = 8
——————————————————————
To check:
Total number of children now = 4+ 8 = 12
Where total height of girls now
= 8x 157cm =1256cm
Total height of children
= 700cm (4boys) + 1256cm
=1956cm
Average ht of children = 1956/12 = 163cm (therefore answer is correct, with 8 girls)
Average height of boys = 700cm/4 = 175cm
B) given the”new “ average height now after boys are added = 163cm
Difference in the average height of boy now is
= 175cm -163cm = 12cm decrease
Difference in an avg ht of a girl now
= 163cm -157cm =6cm
12 / 6= 2
Since the average height of boys is “decreased” this tells us there has to be more girls than boys. Therefore number of girls = 4x 2 = 8
——————————————————————
To check:
Total number of children now = 4+ 8 = 12
Where total height of girls now
= 8x 157cm =1256cm
Total height of children
= 700cm (4boys) + 1256cm
=1956cm
Average ht of children = 1956/12 = 163cm (therefore answer is correct, with 8 girls)
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