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#