Blanco Media and More sell blank audio CDs for $2 each and blank DVDs for $3 each. Which inequality best describes the number of audio CDs, a, and the number of DVDs, d, that can be purchased for $30 or less?

A. 2a + 3d ≤ 30
Correct! In this answer the number of audio CDs, a, is multiplied by its cost, $2, and the number of DVDs, d, is multiplied by its cost, $3. The sum of these products is less than or equal to $30.

B. 2a + 3d < 30
Incorrect. The sum of these products should be less than or equal to $30.

C. 2d + 3a ≤ 30
Incorrect. Multiply the number of audio CDs, a, by its cost, $2. Multiply the number of DVDs, d, by its cost, $3. The sum of these products should be less than or equal to $30.

D. 2d + 3a < 30
Incorrect. Multiply the number of audio CDs, a, by its cost, $2. Multiply the number of DVDs, d, by its cost, $3. The sum of these products should be less than or equal to $30.

Cindy has a budget of $67 to spend on clothes. The sweaters she wants are on sale for $11 each, and the skirt she likes cost $15. All prices include tax. Which inequality could be used to find, s, the maximum number of sweaters Cindy can buy if she also buys one skirt?

A. 11s − 15 ≤ 67
Incorrect. Multiply the cost of each sweater, $11, by the number of sweaters, s. Add $15 for the skirt. All of this must be less than or equal to $67.

B. 15s + 11 < 67
Incorrect. Multiply the cost of each sweater, $11, by the number of sweaters, s. Add $15 for the skirt. All of this must be less than or equal to $67.

C. 26s < 67
Incorrect. Multiply the cost of each sweater, $11, by the number of sweaters, s. Add $15 for the skirt. All of this must be less than or equal to $67.

D. 11s + 15 ≤ 67
Correct! The cost of each sweater, $11, is multiplied by the number of sweaters, s. The cost of the skirt, $15 is added. All of this must be less than or equal to $67.

It takes Robert 0.5 hours to unload boxes from a small delivery truck. It takes 0.75 hours to unload a large delivery truck. Which inequality could be used to find the number of large trucks, l, and the number of small trucks, s, that Robert can unload before the end of his 6 hour shift?

A. (0.5 + s) + (0.75 + l) < 6
Incorrect. Multiply the time it takes to unload a small truck, 0.5 hour, by the number of small trucks, s. Add this to the product of the large truck unloading time, 0.75 hour, and the number of large trucks, l. This sum should be less than 6 hours.

B. 0.5s + 0.75l < 6
Correct! The time it takes to unload a small truck, 0.5 hour, is multiplied by the number of small trucks, s. Add this to the product of the large truck unloading time, 0.75 hour, and the number of large trucks, l. This sum is less than 6 hours.

C. 0.5l + 0.75s < 6
Incorrect. Multiply the time it takes to unload a small truck, 0.5 hour, by the number of small trucks, s. Add this to the product of the large truck unloading time, 0.75 hour, and the number of large trucks, l. This sum should be less than 6 hours.

D. 0.5l + 0.75s > 6
Incorrect. Multiply the time it takes to unload a small truck, 0.5 hour, by the number of small trucks, s. Add this to the product of the large truck unloading time, 0.75 hour, and the number of large trucks, l. This sum should be less than 6 hours.

An apple provides approximately 81 calories, and a banana provides approximately 105 calories. Mary Helen wants to consume no more than 400 calories eating apples and bananas. Which inequality best represents the number of apples, x, and the number of bananas, y, that Mary Helen can eat and stay within this limit?

A. 81x + 105y ≤ 400
Correct! The number of apples, x, times 81 plus the number of bananas, y, times 105 must be less than or equal to 400.

B. (81 + 105)(x + y) < 400
Incorrect. The number of apples, x, times 81 plus the number of bananas, y, times 105 must be less than or equal to 400.

C. 81x + 105y > 400
Incorrect. The number of apples, x, times 81 plus the number of bananas, y, times 105 must be less than or equal to 400.

D. 81x + 105y ≥ 400
Incorrect. The number of apples, x, times 81 plus the number of bananas, y, times 105 must be less than or equal to 400.