Linear inequalities in one or two variables SAT question

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.