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F.3 mathz1問(percentage change)! 吾該幫幫忙!
發問:
plz help me to answer the following questions;;i need the steeps;;thz for your help=)1)If the radius of a circle is increased by 10%,find the percentage increase in its area.2)If the height of a triangle is increased by 30% while its base is dreased by 25%,what is the percentage change in its... 顯示更多 plz help me to answer the following questions;;i need the steeps;;thz for your help=) 1)If the radius of a circle is increased by 10%,find the percentage increase in its area. 2)If the height of a triangle is increased by 30% while its base is dreased by 25%,what is the percentage change in its area? 3)There are 800 students in a school,37.5% of them are girls.If the number of boys and girls are increased by 20% and 10% respectively,What is the percentage change in the number of students?
最佳解答:
Q.1 Area of circle is 3.14 x (R^2), if R is increased by 10%, then the new area should be:- = 3.14 x (R+10%)^2 = 3.14 x (1.1R)^2 = 3.14 x 1.21 x R^2 So, the area is increased by 21% Q.2 Area of triangle is (h x b) / 2, if h is increased by 30% and base is decreased by 25%, the new area should be:- = (h+30%) x (b-25%) / 2 = (1.3h x 0.75b) / 2 = ( 0.975 h x b ) / 2 So, the area is decreased by 2.5% Q.3 Original number of girl = 800 x 37.5% = 300 Original number of boy = 500 New number of girl = 300 x (1+10%) = 330 New number of boy = 500 x (1+20%) = 600 So, new number of total students = 930 % change = (930-800) / 800 x 100% = 16.25%c (increased)
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