1) A contractor mixes concrete from bags of pre-mix for small jobs. How many bags with 6% cement should he mix with 4 bags of 21% cement to produce a mix containing 11% cement?
2) The sum of Two Numbers is 72, and twice their difference is 24. What is the smaller of the two numbers?
3) The Perimeter of a rectangle is 72m. If the width were doubled and the length were increased by 23m, then the perimeter would be 148m. What are the dimensions?
2007-06-10 14:04:24 · 2 answers · asked by Hector 1 in Science & Mathematics ➔ Mathematics
1) 21.4 + 6.x = 11(x+4)
84 + 6x = 11x + 44
5x = 40
x = 8
Answer: 8 bags
2) x + y = 72
x - y = 24
x = 24 + y
24 + y + y = 72
2y = 48
y = 24
The smaller number is 24.
3) 2x + 2y = 72
4x + 2y + 23 = 148
2y = 72 - 2x
4x + 2y = 125
4x + 72 - 2x = 125
2x = 53
x = 53/2
x = 26,5
2y = 72 -2x
y = 36 - x
y = 36 - 26,5
y = 9,5
The dimensions is 9,5m x 26,5m
2(26,5)+ 2(9,5) = 72
2007-06-10 14:19:31 · answer #1 · answered by Carlos 3 · 0⤊ 0⤋
.06x + .21*4 = .11(x+4)
.06x + .84 = .11x +.44
.4 = .05x
x = 8
x = 1 number
72-x = other number
2(72-x-x)=24
144-4x = 24
120= 4x
x = 30
72-x = 42
2l+2w = 72
2(l+23) +4w = 148
2l+46 +4w = 148
2l +4w =102
-2w = - 30
w = 15
l = 21
2007-06-10 14:23:31 · answer #2 · answered by ironduke8159 7 · 0⤊ 0⤋