Answer:
30
Explanation:
Here's our facts:
-There are 3 boys for every 4 girls on the swim team.
-When we add the number of boys to the number of girls on the swim team, we should get the total number of members, which is 70.
Here's what we're looking for:
To find the number of boys, we need to find the number of members of each gender that follows that ratio and also adds up to 70.
The first thing I think about is what the smallest number of members could be. Ratios are usually completely simplified---in other words, the fraction 3/4 can't be simplified any further while still using whole numbers.
To find out the smallest number of members, I added up the 3 boys and 4 girls in the ratio to get a minimum total of 7 members. Here, the ratio is correct---3 boys for every 4 girls---but the number of members is way too small. We want 70, not 7. Notice, however, that 7 goes into 70 exactly 10 times. This is good news! It means that the math will be easier.
The next thing I do with this information is multiply the number of boys and the number of girls by 10 each. Just like when you multiply a fraction by the same number in the numerator and the denominator, the actual value of the fraction doesn't change, it just looks more complex. This gives me 30 boys and 40 girls, which adds up to a total of 70 members. Yay! You'll notice that 30/40 simplifies to 3/4, which means that the ratio of boys to girls is still correct.
Your answer is simply the number of boys, which is 30.
Let me know if you need me to explain anything in a different way!