Question

ivan can paint 25 square feet every half hour. how many square feet can he paint in 3 hours?
○ 225 square feet
○ 150 square feet
○ 75 square feet
○ 50 square feet

Explanation:

Step1: Find the number of half - hours in 3 hours

Since 1 hour has 2 half - hours, in 3 hours, the number of half - hours is $3\times2 = 6$? Wait, no, wait. Wait, the rate is 25 square feet per half - hour. Wait, no, let's re - examine. Wait, the problem says "every half hour" he paints 25 square feet. So first, find how many half - hours are in 3 hours. Since 1 hour = 2 half - hours, then 3 hours have $3\times2=6$ half - hours? Wait, no, that can't be right. Wait, no, wait, maybe I made a mistake. Wait, no, let's check again. Wait, the options are 225, 150, 75, 50. Wait, maybe the rate is 25 square feet per half - hour, so in 1 hour (2 half - hours), he paints $25\times2 = 50$ square feet. Then in 3 hours, he paints $50\times3=150$ square feet. Let's do it step by step.

Step1: Calculate the number of half - hours in 3 hours

We know that 1 hour = 2 half - hours. So for 3 hours, the number of half - hours $n=3\times2 = 6$? Wait, no, that would be wrong because if he paints 25 per half - hour, 6 half - hours would be $25\times6 = 150$. Yes, that matches one of the options. Wait, let's correct the step.

Step1: Determine the number of half - hour intervals in 3 hours

Since 1 hour contains 2 half - hours, the number of half - hours in 3 hours is $3\times2=6$? No, wait, no. Wait, half - hour is 0.5 hours. So the number of half - hour periods in 3 hours is $\frac{3}{0.5}=6$.

Step2: Calculate the total area painted

The rate is 25 square feet per half - hour. So the total area $A$ painted in 3 hours is the rate per half - hour times the number of half - hours. So $A = 25\times6=150$ square feet.

Answer:

150 square feet (the option with "150 square feet")