You and a friend buy two fruit smoothies and leave a tip. You split the total and your half comes to $3.60. What percent tip (in decimal form) did you and your friend leave if the fruit smoothies cost $3 each?

Let us first find what the total amount is. It is 3.60 + 3.60 = 7.20

Now let us find the cost of two fruit smoothies. It is 3+3 = 6

So the tip left by you = 7.20 - 6 = 1.20

That is, $1.20 tip for an amount of $7.20

To change it into a percent, form a fraction using the above two numbers and multiply it by 100.

So, the fraction is 1.20/7.20 (Numerator 1.20 and denominator 7.20)

Now multiply by 100

1.20/7.20 X 100 = 16.67

the amount they paid includes the price of the two smoothies and tip

since the friends are splitting the bill in 2, then each friend pays only half the amount

each friend pays $ 3.60 each

so the total amount they both paid is 3.60 x 2 = $ 7.20

the cost of one smoothie - $3

therefore the cost of the 2 smoothies - 3 x 2 = $ 6

so they paid 7.20 but the bill was only 6 dollars

so the difference in the 2 amounts is the value of the tip they left

tip = 7.20 - 6 = 1.20

so the percentage of the tip is - tip amount / value of the bill x 100 %

percentage = 1.20 / 6.0 x 100 % = 20 %

they left 20 % of the bill as a tip