Question

a high - speed elevator can rise 480 feet in 30 seconds. which expression represents the rate, in feet per minute, of the elevator? 480×30; 480×2; 480÷2; 480÷30

Explanation:

Step1: Understand the time conversion

We know that 30 seconds is half a minute (since 1 minute = 60 seconds, and 60 ÷ 2 = 30). To find the rate in feet per minute, we can either convert the time to minutes first or find the rate per second and then multiply by 60. But another way: if in 30 seconds (0.5 minutes) it goes 480 feet, then in 1 minute (which is 2 times 30 seconds), the distance would be 480 × 2. Let's check the rate formula: rate = distance / time. If we want feet per minute, time should be in minutes. 30 seconds is 0.5 minutes. So rate = 480 / 0.5 = 480 × 2 (because dividing by 0.5 is multiplying by 2). Alternatively, if we first find feet per second: 480 ÷ 30, then multiply by 60 to get per minute: (480 ÷ 30) × 60 = 480 × 2. So the expression is 480 × 2.

Step2: Analyze each option

• Option 480 × 30: This would be incorrect as it's multiplying distance by time, not related to rate.
• Option 480 × 2: As explained, this gives the distance in one minute (since 30 seconds × 2 = 60 seconds = 1 minute), so this is correct.
• Option 480 ÷ 2: This would be dividing distance by 2, which doesn't make sense for rate per minute.
• Option 480 ÷ 30: This is the rate in feet per second, not per minute.

Answer:

B. 480 × 2 (assuming the options are labeled as A: 480 × 30, B: 480 × 2, C: 480 ÷ 2, D: 480 ÷ 30)