Question

A group of friends went out for dinner and decided to split the cost of the bill equally. If each person contributed $32, the friends would have $18 more than they needed for the bill but not enough for a 15% tip. If each person contributed $35, they would cover the bill and a 15% tip and have $6.30 left over. How much was the bill, and how many friends went out for dinner?

Answer 1

The number of friends that went out for dinner is 8

And their bill is $238

Explanation:

Let's assume that the number of friends that went out for dinner to be x

And the bill for the dinner to be y

If each person contributed $32 and paid off the bill,they will have a balance of $18

32x - 18 = y_____equation 1

If each person contributed $35 and paid off the bill and also 15% tip,they will have a balance of $6.30

35x - 6.3 = y + (15% of y)

35x - 6.3 = y + (3y/20)

Open up the bracket

35x - 6.3 =(20y + 3y)/20

700x - 126 = 23y______equation 2

From equation 1,y = 32x - 18

Put the above in equation 2 and we have

700x - 126 = 23(32x -18)

700x - 126 = 736x - 414

collect like terms

36x = 288

x = 288/36

x = 8

Remember that equation 1 says that y = 32x - 18 and we now know that x = 8 .

Substitute and we have

(32 × 8) - 18

y = 238

The number of friends that went out for dinner is 8

And their bill is $238