Need help with this math question

Question

Company X has a mobile app for both iPhone and Android. Overall they have 1,000,000 users who log onto the app an average of 15 times a month. The average iPhone user logs in 9 times a month whilst an average Android user logs in 19 times a month.

1. Calculate the number of users who access the app with an iPhone
2. If the number of app users (1,000,000) remains the same, and the overall logins increased by 20% and iPhone logins increased by 2/3rd, what share of users come from Android login?

Answer 1

Iphone users + Android users = 1,000,000

Usage / 1,000,000 = 15

So, total usage is 15,000,000 per month

Iphone users only log in 9 times per month, while Android users log in 19 times per month

So, Iphone * 9 + Android * 19 = 15,000,000

Now we have two equations with two unknowns and can solve with either substitution or elimination. Or, if you're allowed the use of a graphing calculator, by graphing.

Let's see this one by elimination. We have:

Iphone users + Android users = 1,000,000

Iphone * 9 + Android * 19 = 15,000,000

We need to multiply the top equation by either 9 or 19 and then subtract.

(Some teachers have you multiply by negative 9 and then add, which can help)

Iphone*19 + Android *19 = 19,000,000

- ( Iphone * 9 + Android * 19 = 15,000,000)

______________________________________

iphone*10 = 4,000,000

so they have only 400,000 monthly iphone users and 600,000 monthly android users

For part two, rerun everything with 18 million monthly logins and iphone users at 15 logins per month.

Message me if you want this run through differently, or if you just need to hear it and ask questions.