Here we have 3 general algebraic problems that we need to solve. Using simple reasoning we can solve these.
1) L = 4.4 ft
2) This month you used 645.85 KW-h in your home.
3)Cost = $19.44
1) You will buy a board of length L.
You will cut two pieces that are 1.4 ft long.
So at this point, the length of the board piece is:
L - 1.4ft - 1.4ft = L - 2.8ft.
Now, you want this to be 1.17 times longer than 1.4ft, then we need to solve:
L - 2.8ft. = 1.17*(1.4ft) = 1.638ft
L = 1.638ft + 2.8ft = 4.438ft
Rounding to the nearest tenth, we get:
L = 4.4 ft
This is the length of board you should buy.
2) Here we know:
You pay $0.13 per KW-h
This month, you pay a total of $83.96
The total number of KW-h you used is equal to the quotient between the total amount you paid and the price of a single KW-h, this is:
N = $83.96/$0.13 = 645.85
This month you used 645.85 KW-h in your home.
3) Here we know:
You pay $0.09 per KW-h.
Running the bulb for one hour consumes 0.06 KW-h
So, if you leave one of these lights on all day (24 hours) it would consume:
24*0.06 KW-h = 1.44 KW-h
If you instead leave 5 of these bulbs, you will consume 5 times that amount:
5*1.44 KW-h = 7.2 KW-h
This is in one single day, if you do this for 30 days, the total consumption is:
30* 7.2 KW-h = 216 KW-h
And you pay $0.09 for each one of these, then the cost is 216 times $0.09
Cost = 216*$0.09 = $19.44
If you want to learn more about algebra, you can read:
https://brainly.com/question/24382046
