可否清楚例明計算下面問題既step?

There were 510 boys and 390 girls in a school last year. If the numbers of boys and girls have increased by 10% and 20% respectively this year, find the total number of students in the school this year. Find also the percentage increase.

Total number of students
510 x (1+10%) + 390 x (1+20%)
= 510 x 110% + 390 x 120%
= 561 + 468
= 1029 students

Percentage Increase
[1029 – (510+390)] / (510+390) x 100%
= (1029 – 900) / 900 x 100%
= 129 / 900 x 100%
= 0.1433 x 100%
= 14.33% (小數點後兩個位)

total number students in the school this year:
510x(1+10%)+390x(1+20%)
=510x110%+390x120%
=561+468
=1029
percentage increase:
[1029-(510+390)]/(510+390)
=[1029-900]/900
=129/900
=14.33%

The boys in the school in this year are

510*110% = 561

The girls in the school in this year are

390*120% = 468

The total number of students in the school this year are

561+468 = 1029

The percentage increase is

1029 - (510+390) / (510+390) *100%

=14.3%,cor.to 3 sig.fig

如果唔信答案既話 可以驗証下 一定岩

total number of boys :
510 x ( 1 + 10% ) = 510 x 1.1 = 561

total number of girls :
390 x ( 1 + 20%) = 390 x 1.2 = 468

total number of studetns :
total number of boys + total number of girls = 561 + 468 = 1029

percentage increase :

1029 / ( 510 + 390 ) - 1 = 0.143 = 14.3%