Ken is working this summer as part of a crew on a farm. He earned $8 per hour for the first 10 hours he worked this week. Because of his performance, his crew leader raised his salary to $10 per hour for the rest of the week. Ken saves 90% of his earnings from each week. What is the least number of hours he must work the rest of the week to save at least $270 for the week?
ken initially earns $8 per hour, during the first 10 hours he earned 8 x 10 = $80
For the remaining x hours, he will get a raise to $10 per hour, earning him $10x
Also, Ken saves 90% of all the money he earned.
If he plans to save at least $270, he must work for: 0.9(10x + 80) ≥ 270 hours
9x + 72 ≥ 270
9x ≥ 270 - 72
9x ≥ 19
x = 198/9
x = 22
Thus, he must work 22 hours to save at least $270
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