sat suite question viewer
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?
Explanation
Choice C is correct. Ken earned $8 per hour for the first 10 hours he worked, so he earned a total of $80 for the first 10 hours he worked. For the rest of the week, Ken was paid at the rate of $10 per hour. Let x be the number of hours he will work for the rest of the week. The total of Ken’s earnings, in dollars, for the week will be 
. He saves 90% of his earnings each week, so this week he will save 
dollars. The inequality 
represents the condition that he will save at least $270 for the week. Factoring 10 out of the expression gives 
. The product of 10 and 0.9 is 9, so the inequality can be rewritten as 
. Dividing both sides of this inequality by 9 yields 
, so 
. Therefore, the least number of hours Ken must work the rest of the week to save at least $270 for the week is 22.
Choices A and B are incorrect because Ken can save $270 by working fewer hours than 38 or 33 for the rest of the week. Choice D is incorrect. If Ken worked 16 hours for the rest of the week, his total earnings for the week will be 
, which is less than $270. Since he saves only 90% of his earnings each week, he would save even less than $240 for the week.