To find the number of buses, divide the total number of students by the capacity of one bus: \(115 \div 25 = 4\) with a remainder of 15. This means 4 buses will be completely full, but there will be 15 students left over. To transport these remaining students, one more bus is needed. Therefore, a total of \(4 + 1 = 5\) buses are required.

First, find the total number of days in 3 weeks: \(3 \text{ weeks} \times 7 \text{ days/week} = 21 \text{ days}\). Then, multiply the total number of days by the number of hours in a day: \(21 \text{ days} \times 24 \text{ hours/day} = 504 \text{ hours}\).

First, find the cost of a single hat by dividing the total cost by the number of hats: \($72 \div 6 = $12\) per hat. Next, multiply the cost per hat by the new quantity of hats: \($12 \times 4 = $48\).

This is a multi-step work rate problem where you need to calculate how much each person accomplishes over time, then find the difference.

Start by finding how many boxes each person packs in 4 hours. Leo packs 15 boxes per hour, so in 4 hours he packs $$15 \times 4 = 60$$ boxes. Mia packs 12 boxes per hour, so in 4 hours she packs $$12 \times 4 = 48$$ boxes. The difference is $$60 - 48 = 12$$ boxes, making D correct.

Let's examine why the other answers are wrong. Choice A (3 boxes) represents the difference in their hourly rates (15 - 12 = 3), but this ignores that they worked for 4 hours. Choice B (108 boxes) is the total number of boxes both workers packed combined (60 + 48 = 108). This is a common trap where students add instead of finding the difference. Choice C (27 boxes) appears to be a calculation error, possibly from incorrectly multiplying the rate difference by hours and adding extra (3 × 4 = 12, then somehow getting to 27).

When you see work rate problems asking "how many more," always follow this pattern: calculate each person's total output over the given time period, then subtract to find the difference. Don't just look at the difference in rates per hour—you must account for the total time worked. The key is recognizing that rate differences get magnified over longer work periods.

To find the number of shelves needed, divide the total number of books by the number of books each shelf can hold: \(392 \div 28\). Performing the division: \(392 \div 28 = 14\). Since there is no remainder, exactly 14 shelves will be completely filled.

First, find the total number of slices. There are 5 pizzas with 8 slices each, so there are \(5 \times 8 = 40\) slices in total. Then, divide the total number of slices by the number of players: \(40 \div 10 = 4\) slices per player.

First, find out how many shells each friend received. Divide the total number of shells by the number of friends: \(96 \div 4 = 24\) shells per friend. Sarah starts with 24 shells. Then, she gives away 7, so she has \(24 - 7 = 17\) shells left.

First, calculate the total number of toys produced in one day: \(45 \text{ toys/hour} \times 8 \text{ hours} = 360 \text{ toys}\). Next, divide the total number of toys by the number of toys per box to find how many boxes are filled: \(360 \div 15 = 24\) boxes.

First, calculate the total number of apple trees: \(18 \times 15 = 270\) apple trees. Next, calculate the total number of pear trees: \(12 \times 10 = 120\) pear trees. Finally, find the difference between the number of apple trees and pear trees: \(270 - 120 = 150\).

First, find David's rate of solving problems. He solves \(16 \div 8 = 2\) problems per minute. To find how many he can solve in 20 minutes, multiply his rate by the new time: \(2 \times 20 = 40\) problems.