three teenagers can eat 6 pizzas in half an hour. Assuming that their friends eat at the same rate, how many pizzas can 5 teenagers eat in 90 minutes?

6pizza/(3teen*.5hr) = 4pizza/(teen-hr)

so, that's 4 pizzas per hour per teen

take that and use the given data to get the final number of pizzas:

4pizza/(teen*hr) * 5teen * 1.5hr = 30pizza

To find out how many pizzas 5 teenagers can eat in 90 minutes, we can set up a proportionality equation based on the information given.

First, let's determine the rate at which three teenagers can eat pizzas in half an hour. We know that three teenagers can eat 6 pizzas in half an hour, so we can write this as a ratio:

(3 teenagers)/(6 pizzas) = (t) teenagers / (0.5) hours

Now, let's determine the rate per teenager per hour. To do this, we need to divide the ratio by the number of teenagers:

(3 teenagers)/(6 pizzas) ÷ 3 = (t) teenagers / (0.5) hours ÷ 3

Simplifying, we get:

1 teenager / 2 pizzas = (t) teenagers / (0.5) hours ÷ 3

Now, we can find the rate at which 1 teenager can eat pizzas in 1 hour:

(1 teenager) / (2 pizzas) = (t) teenagers / (0.5) hours ÷ 3 × 1 hour

Simplifying, we get:

1 teenager / 2 pizzas = (t) teenagers / (1.5) hours

Now, we can use this ratio to find out how many pizzas 5 teenagers can eat in 90 minutes:

(5 teenagers) / (x pizzas) = (1 teenager) / (2 pizzas)

By cross-multiplying, we get:

(5 teenagers) × (2 pizzas) = (1 teenager) × (x pizzas)

10 pizzas = x pizzas

Therefore, 5 teenagers can eat 10 pizzas in 90 minutes.