中一數學1題

In Mongkok,18 families want to have two or more children.
(120*15%=18)

In Yuen Long,70 families want to have two or more children.
(200*35%=70)

There are 88 families want to have two or more children in these two districts.
(70+18=88)

There are 320 families have been interviewed in these two districts.
(200+120=320)

So,the percentage of the interviewed families want to have two or more children in these two districts=27.5%
(88/320=0.275=27.5%)

In Mongkok, families have been interviewed and want to have two or more childred:-

120 x 15% =18

In Yuen Long, families have been interviewed and want to have two or more childred:-

200 x 35% = 70

In total familes have been interview and want to have two or more children:-

for Mongkok 18/(120+200) % = 5.625%

for Yuen Long 70/(120+200) % = 21.875%