$65.32 is 115% of the bill, so set up a proportion:

65.32/x = 115/100

To solve: 100×65.32 = 6532. 6532/115 = 56.8, or $56.80.

#2

Average is all the grades added up divided by the number of grades present. So set up an inequality, using “x” in place of the unknown grade.

(75+63+68+x)/4 >_ 70 … (>_ should be the greater than or equal to sign)

Solve for x. Multiply both sides by 4, then subtract 75, 63, and 68 from both sides, giving you 74, so Sam needs a 74 or higher to get a C.

The amount of $65.32 means that the bill was most probably somewhere between $50 and $60, right? So start with $50 x .15 and add the answer to $50. If the total is below $65.32, try $60 x .15. If $60 x .15 added to $60 is too high, then your answer lies somewhere between the $50 and $60. Start with the middle: $55 x .15. If that’s too low, try $56 x .15, and if that’s still too low, try $57 x .15. If that’s too high, the answer lies somewhere between $56 and $57.

So, start the process with $56.50, then go up or down, depending on the answers you’ve gotten, adding or subtracting ten cents each time until you get the amount of $65.32. (If you can’t get the exact figure of $65.32 by adding or subtracting ten cents, then find the two numbers where $65.32 falls and try adding five cents to the number you are multiplying by .15 until you get $65.32 right on the button.)

I’m sure someone else will give you a much easier mathematical approach to this problem, but if you’re mathematically challenged, the good, old-fashioned common-sense approach, though it takes longer, will get you through in a pinch.

Good luck – 🙂

Oh, and the second one: same common-sense approach, starting with a good, educated guess. My first guess was that he would need a 75 on his final test, and, what do you know, 75 + 63 + 68 + 75 = 281. Since 281 divided by the four grades = 70 with one extra point, knock that one point off the 75 we gave him and give him a 74 on the final test. 74 + 63 + 68 + 74 = 280. And 280 divided by 4 = a perfect 70, which gives him the C he needs.

So here is how i did it:

1) 65.32* 0.75= 48.99 <- the cost of meal alone Did times 0.75 cause that's the price of the meal, not the tip 2) (x+75+65+68) is greater or equal than 280 (multiplied 4 both sides!) subtract 75, 65, and 68 on both sides to get 74 Answer: X is greater or equal than 74 show greater or equal by a > and = beneath it.

Have a good day!