Final answer:
To find the number of tablespoons of butter needed for thirty rolls, set up a proportion based on the given recipe. Solve the proportion to find that 7.5 tablespoons of butter are needed for thirty rolls.
Step-by-step explanation:
The student is dealing with a simple proportion problem in mathematics. To find out how many tablespoons of butter are needed for thirty rolls, you set up a proportion using the initial condition that 20 rolls require 5 tablespoons of butter. The proportion is as follows:
20 rolls / 5 tablespoons = 30 rolls / x tablespoons,
where x is the number of tablespoons needed for 30 rolls. To solve for x, you cross-multiply and get:
20x = 5 × 30,
20x = 150,
Then, divide both sides by 20 to solve for x:
x = 150 / 20,
x = 7.5 tablespoons of butter.
Therefore, the student needs 7.5 tablespoons of butter for thirty rolls.