rachelmaddie
Full Member
- Joined
- Aug 30, 2019
- Messages
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Hi, can someone please check this for me?
The boat travels 2.4 miles downstream with the speed of (21+x) miles per hour.
Let x miles per hour represent the current of the river.
2.4/21 + x hours
The boat travels 1.8 miles upstream with the speed of (21-x) miles per hour.
1.8/21 - x hours
The time is the same in the equation
2.4/21 + x = 1.8/21 - x
Cross multiply:
2.4(21 - x) = 1.8(21 + x)
Multiply by 10:
24(21 - x) = 18(21 + x)
Divide by 6:
4(21 - x) = 3(21 + x)
84 - 4x = 63 + 3x
84 - 63 = 3x + 4x
7x = 21
x = 3 mph
Solution: 3 miles per hour
The boat travels 2.4 miles downstream with the speed of (21+x) miles per hour.
Let x miles per hour represent the current of the river.
2.4/21 + x hours
The boat travels 1.8 miles upstream with the speed of (21-x) miles per hour.
1.8/21 - x hours
The time is the same in the equation
2.4/21 + x = 1.8/21 - x
Cross multiply:
2.4(21 - x) = 1.8(21 + x)
Multiply by 10:
24(21 - x) = 18(21 + x)
Divide by 6:
4(21 - x) = 3(21 + x)
84 - 4x = 63 + 3x
84 - 63 = 3x + 4x
7x = 21
x = 3 mph
Solution: 3 miles per hour