Math help...my answers inside?

Question

Subtract
Susan began a trip with 18 ½ gallons of gas in the gas tank of her car. If she used 17 ¾ gallons on the trip, how many gallons did she have left when she finished the trip?
___ Gallon

18 ½ x 4

17 ¾ x 2

4/8
6/8

18 4/8
17 6/8

1 2/8

2/4
¾

Subtract (enter as an improper fraction)
The canister contained 6 1/8 cups of flour when Mary started making cookies. Mary used 2 ½ cups. How many cups were left in the canister?
____ Cups

6 1/8
2 1/2

1/8 x 2
1/2 x 8

2/16
8/16

6 2/16
2 8/16
4 6/16

Multiply
Find the number of bushels of wheat to be harvested from 12 ¾ acres if each acre yields 36 bushels.
____ Bushels

12 3/4
36
(No idea… need some help)

Multiply
Sarah gives each of five friends 1/8 of a pie. How much of the pie does she give them altogether?
___ Pie

5
1/8
(No idea… need some help)

I attempted the top two but once it got to multiply I got lost...

Answer 1

Question 1

1)Turn the numbers into simple fractions
18 1/2 becomes 37/2 and 17 3/4 becomes 71/4

2)Now, change to a common denominator, in this case four
37/2 becomes 74/4

3) Now, just subtract 74/4-71/4 = 3/4

Question 2 (uses the same system)

1) Change to simple fractions so 6 1/8 becomes 49/8 and 2 1/2 becomes 5/2.
2) Change to common denominator of 8, so 5/2 becomes 20/8.
3) Now subtract. 49/8 - 20/8 = 29/8 or 3 5/8

Question 3

The key to this one is changing 36 bushels into a fraction, which would be 36/1.

1) Change 12 3/4 into a simple fraction, so it becomes 51/4.
2) Now multiple across. 51 x 36 = 1836 4 x 1 = 4
3) The answer is 1836/4, or simplied as 459 (divide 1836 by 4).

Question 4

Solved the same way as question 3.

1) change the number 5 to a fraction, so it becomes 5/1.
2) Now multiply 5/1 and 1/8 across so that 5 x 1 = 5 and 1 x 8 = 8
3) The answer is 5/8.

Answer 2

18-1/2 gallons, used 17-3/4 gallons:

18-1/2 = ((18 x 2) + 1) / 2 = 37/2 = 74/4
17-3/4 = ((17 x 4) + 3) / 4 = 71/4
18-1/2 - 17-3/4 = 74/4 - 71/4 = 3/4 gallons left


6-1/8 cups, used 2-1/2

6-1/8 = ((6 x 8) + 1) / 8 = 49/8
2-1/2 = ((2 x 2) +1) / 2 = 5/2 = 10/4 = 20/8
6-1/8 - 2-1/2 = 49/8 - 20/8 = 29/8 = 3-5/8 cups left


1 pie cut in 8 slices, 5 are given

1 pie has 8 pieces = 8/8
5 slices of 1/8 given away = 5/8
8/8 - 5/8 = 3/8 slices left

Answer 3

Bushels question:
for 3/4 bushel you divide 3 by 4 to get .75 so you need to find out how many bushels for 12.75 acres X 36 bushels per acre = 459

If each friend gets 1/8 then you add 1/8+1/8+1/8+1/8+1/8=5/8 (since you're adding the same number 5 times it can be done as multiplication as 5X1/8=5/8)

P.S. your subtraction on the flour question is wrong, the answer is actuall 3 6/16 which can be reduced to 3 3/8

Answer 4

1) 18 ½ - 17 ¾

18 4/8 - 17 6/8

1 - 2/8 = 8/8 - 2/8 = 6/8 = 3/4

you forgot the minus sign (4-6)/8 = -2/8 not 2/8

2) same mistake here

6 2/16 - 2 8/16 = 4 - 6/16
64/16 - 6/16 = 58/16 = 3 10/16

3) (12 3/4) X 36 = (51/4) X 36 = 1836/4 or 459

4) 5 x 1/8 = 5/8

Answer 5

1. (3/4) You got your math right! Good job!

2. (3 5/8) Find the common denominator, subtract then reduce the improper fraction

3. (459 bushels) 12 3/4 x 36=
12.75 x 36= 459.00

4. (5/8 total) 5 x 1/8=
5/1 x 1/8= 5/8