# SAT Math Multiple Choice Practice Question 549: Answer and Explanation

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**Question: 549**

**6.** If it costs *z* dollars to buy *n* pizzas, how much will it cost, in dollars, to buy *b* pizzas at the same rate?

A.

B.

C.

D.

E. *znb*

**Correct Answer:** A

**Explanation:**

**A** This is a great problem for Plugging In. Let's try using *z* = 2, *n* = 5, and *b* = 15. If $2 will buy 5 pizzas, then how much will 15 pizzas cost? Three times the number of pizzas will have three times the cost, so $6. Now you just need to figure out which choice will give you $6. Try calculating each of the answer choices, and you'll find that only A equals $6.