A cell phone company offers text message plans where the number of texts allowed varies directly with the amount of money paid. Their most popular plan is 400 texts for $8. How many text messages are included in the plan that costs $10? 500, 600, 700, 800

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Answer 1 · 2018-06-23T15:17:37

$500$

Since the amount of text messages varies directly with the amount of money paid, it will be proportional.

So set up a proportion:

$"number of text messages"/"amount of money"$ $= 400/8$

The second plan will be proportional to the first one, so here is the resulting equation:

$400/8 = x/10$

The number of text messages in the second plan is not known, so I gave it the variable $x$ . However, the amount of money is known.

Now cross multiply to solve:

$400/8 = x/10$

$400 xx 10 = x xx 8$

$4000 = 8x$

$500 = x$

So the amount of messages included in the second plan is $500$