1) Brass is made up of 68% copper and 32% zinc by weight.
If a brass box weights 35 kg,find the weights of copper in the box.
2) David spends 45 minutes on maths homework and this makes up
20% of his total time spent on school homework. How many hours
does David spend on his school homework?
Both are not equations .
2006-11-08 12:24:17 · 3 個解答 · 發問者 -3- 3 in 科學 ➔ 數學
1)
Weight of brass box=35kg
percentage of copperin the brass box=68
Weight of copper in the box= 35X0.68= 23.8kg
2)
Time for maths HW=45 min
Percentage of total=20
Total time for HW=45X5=225 min
225/60= 3.75 hours
2006-11-08 12:48:45 · answer #1 · answered by Brian 2 · 0⤊ 0⤋
1) 100% = 35 kg
Copper = 68% of 35kg
= 23.8 kg
(double check) Zinc = 32% of 35 kg
=11.2 kg
23.8 + 11.2 = 35 kg
2) 20% = 45 minutes
1 % = 45/20
= 2.25
100% = 100 x 2.25
= 225 minutes
=3 hrs and 45 minutes
2006-11-08 12:53:02 · answer #2 · answered by Candice Chu 1 · 0⤊ 0⤋
1. 35 X 0.68 = 23.8 kg
2. 45 / 0.2 = 225 minutes
225 / 60 = 3.75 hours
2006-11-08 12:31:24 · answer #3 · answered by ? 7 · 0⤊ 0⤋