First, calculate the total number of days Liam works on the project. There are 7 days in a week, so three weeks is 3 × 7 = 21 days. Next, calculate the total time in minutes: 21 days × 40 minutes/day = 840 minutes. Finally, convert the total minutes to hours by dividing by 60: 840 minutes ÷ 60 minutes/hour = 14 hours.

First, find out how many 5-minute intervals are in one hour. Since there are 60 minutes in an hour, divide 60 by 5: 60 ÷ 5 = 12. So, there are 12 five-minute intervals in one hour. If the train travels 3 miles in each of these intervals, the total distance is 12 × 3 miles = 36 miles.

The first bus arrives at 6:00 AM. The fifth bus arrives after four more 12-minute intervals. The total time elapsed after the first bus is 4 × 12 minutes = 48 minutes. The arrival time of the fifth bus is 6:00 AM + 48 minutes, which is 6:48 AM.

First, the units must be the same. Convert the total distance from meters to centimeters. Since there are 100 centimeters in 1 meter, 3 meters is equal to 3 × 100 = 300 centimeters. To find the time it takes, divide the total distance by the snail's speed: 300 cm ÷ 2 cm/minute = 150 minutes.

First, calculate the total time required to clean all four offices. The time for one office is 1 hour and 15 minutes. For four offices, the total time is 4 × (1 hour and 15 minutes). This is 4 hours and (4 × 15) minutes, which equals 4 hours and 60 minutes. Since 60 minutes is 1 hour, the total time is 5 hours. Finally, add this total time to the start time: 8:30 AM + 5 hours = 1:30 PM.

First, calculate the perimeter of the garden in yards. The formula for the perimeter of a rectangle is P = 2(length + width). So, P = 2(10 + 5) = 2(15) = 30 yards. Next, convert the perimeter to feet: 30 yards × 3 feet/yard = 90 feet. Finally, calculate the total cost: 90 feet × $4/foot = $360.

First, calculate the total number of minutes in a day. There are 60 minutes in an hour and 24 hours in a day. So, there are 60 × 24 = 1,440 minutes in a day. Next, multiply the total minutes by the amount of water wasted per minute: 1,440 minutes × 3 milliliters/minute = 4,320 milliliters.

This is a unit conversion and rounding problem that requires you to work through multiple steps carefully. You need to find the total string needed, convert between units, and determine the minimum whole yards to purchase.

First, calculate the total string needed: Keisha wants to make 9 bracelets, and each requires 8 inches of string. So she needs $$9 \times 8 = 72$$ inches total. Next, convert this to yards since string is sold by the yard: $$72 \text{ inches} \div 36 \text{ inches per yard} = 2$$ yards exactly.

Since Keisha needs exactly 2 yards and must buy whole yards, she needs to purchase 2 yards minimum.

Looking at the wrong answers: Choice A (1 yard) would only give her 36 inches of string, which is far short of the 72 inches she needs. Choice C (3 yards) would work but isn't the minimum required—she'd have 36 extra inches. Choice B (6 yards) is way more than necessary, giving her 216 inches when she only needs 72.

The key insight is that this problem works out to a whole number of yards exactly, so no rounding up is needed. If the calculation had resulted in 2.3 yards, for example, she would need to round up to 3 whole yards.

Strategy tip: In "minimum purchase" problems, always calculate the exact amount needed first, then round UP to the next whole unit if necessary. Watch for problems where the math works out evenly—no rounding may be required.

To solve this problem, both distances must be in the same unit. There are 1,000 meters in 1 kilometer. So, the total length of the race in meters is 5 km × 1,000 m/km = 5,000 meters. To find the remaining distance, subtract the distance Jenna has already run from the total distance: 5,000 meters - 3,500 meters = 1,500 meters.

First, convert the total length of the ribbon to feet. Since 1 yard = 3 feet, 5 yards is equal to 5 × 3 = 15 feet. Next, calculate the total length of the pieces cut off: 3 pieces × 2 feet/piece = 6 feet. Finally, subtract the cut length from the original length: 15 feet - 6 feet = 9 feet.