Calculate the height of a tree whose shadow is 20m shorter when the angle of elevation of the sun is 60° than when it's 30°.

If y varies directly as x2 and y=6 when x=6, find the constant of variation.

If private savings 'v' = 0.75s and total savings 's' equals $4.20 billion, solve for public and private savings.

Money off coupons have been circulated to 300 households. only 2/5 of these were redeemed (used) in the local supermarket to get a free shampoo. what fraction of coupons were unused? (ps: write how you got the answer)