Page 52 - Algebra 1
P. 52

Explanation:
1. Let the still water speed of the boat be x km/hour The speed of the stream is y km/hour
Let the speed of the boat down the stream = x + y Speed of the boat upstream = x – y
20 + 15 =12 𝑥−𝑦 𝑥+𝑦
25 + 30 =17 𝑥−𝑦 𝑥+𝑦
Let1 =pand1 =q 𝑥−𝑦 𝑥+𝑦
20p + 15q = 12...........(1) 25p + 30q = 14............(2) Multiply (1) by 2
60p + 30q = 24
25p + 30q = 17
Subtract the two equations 35p = 7
p=1 5
1=1
𝑥−𝑦 5
5 = (x – y)
5 = x – y......................(3)
25p + 30q = 14 25 × 1 + 30q = 14
5
30q = 9 q=9
q=3 10
1=3
𝑥+𝑦 10
10 = 3x + 3y................(4) Multiply (3) by 3
15 = 3x – 3y
Add the above and (4) 25 = 6x
x = 25 km/hr 6
2. Let the first amount be x Second amount be y 0.12x + 0.15y = 225.6 0.15x + 0.12y = 255
or
0.04x + 0.05y = 75.2 0.05x + 0.04y = 85
30
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 ALGEBRA




































































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