Math
posted by Kim on .
I need serious help. Tried to work it out but I just couldn't get the correct answer.
Benjamin and olivia are putting a new floor in their kitchen. To get the floor up to the desired height, they need to add 1 /8ft to subfloor. They can do this in one of two ways. They can put 1/2in sheet on top of 5/8in board (note that the total would be 9/8ft or 1 /8ft). They could also put 3/8in board on top of 3/4in sheet.
here is a table that gives the price for each sheet of plywood
1/8in $9.15
1/4in $13.05
3/8in $14.99
1/2in $17.88
5/8in $19.13
3/4in $21.36
7/8in $25.23
1in $28.49
1. what is the combined price for a 1/2in sheet and a 5/8 sheet?
2. what is the combined price for a 3/8in sheet and 3/4in sheet?
3. what other combination of sheets of ply wood yields the need 1 1/8in thickness?
4. of the four combinations, which is most economical?
5. the kitchen is to be 12ftx12ft. Find the total cost of the plywood you have suggested in qusetion 4

1. $17.88 + $19.14 = ?
2. $14.99 + $21.36 = ?
3. 1 inch + 1/8 inch
and 7/8 inch + 1/4 inch
This gets you started. If you post your answers, we'll be glad to check them. 
I am trying to reverse engineer your statement.
Do you really mean you need to raise the floor 1 1/8 INCH?
I will have to assume that is what you mean because you said that 1/2 inch + 5/8 inch = 9/8 inch was right
now
1. surely you can add 17.88 and 19.13 = 37.01
2. I am also sure you can add 14.99 and 21.36 = 36.35
3. What else here adds to 9/8?
we could use 1/8+1 (9.15+28.49=37.64)
we could use 7/8+1/4 (25.23+13.05=38.28)
Of course we could use more than two sheets, but the wording of the question implies do not consider the next two:
we could use 9 of 1/8 (9*9.15=82.35)
we could use 3 of 3/8 (3*14.99=44.97)
4. Now the minimum here was 36.35 for a sheet of 3/8 + a sheet of 3/4
5. 12*12 = 144 ft^2
a sheet of plywood is 4*8 = 32 ft^2
so we need 4.5 of these.
If we could get this by the half sheet, the price would be
36.35*4.5 = 163.58 which would be fine for a mathematician but not for a lumber yard which is likely to insist that you buy full sheets, in other words five of each size:
36.35*5 = 181.75 
1 1/15+3 3/102 4/5=