In your Question 3, cost (C) is proportional to the cube of the length (b).
So write a proportionality equation:
C ∞ b^3
Then straight away replace the proportionality sign "∞" with "= k x" - and the x here is multiplication.
So we get:
C = k x b^3
The magic value k is known as the constant of proportionality.
For more info on this topic have a look at
http://community.boredofstudies.org/showpost.php?p=1945405&postcount=2
In your Question 4, remember the table is for a loan of $1000.
So if you borrow $1000 at 7.0% for 20 years, then the table says you have a monthly repayment of $7.75.
But we're borrowing $150 000, not $1000. Since $150 000 is really 150 lots of $1000, we have to make 150 lots of monthly repayments.
So for a loan of $150 000, the monthly repayment is 150 x 7.75 = $1162.50
Does this help?
