Question

1) 60 meters of fencing are needed to fence in a square lot. What is the area of the lot?
a) 3600 m^2
b) 900 m^2
c) 225 m^2
d) 15 m^2

2) A can do a piece of work in r days and B, who works faster, can do the same work in s days. Which of the following expressions, if any, represents the number of days it would take the two of them to do the work if they worked together?
a) r+s/2
b) r-s
c) 1/r + 1/s
d) rs/r+s
e) none of these answer

Answer 1

perimeter = 4 x
so x = 15
area = 225
--------------------
A does task/r per day
B does task/s per day

[ 1/r + 1/s ] task/day together
so
1/ [ 1/r + 1/s ]

= r s / (r+s)
or
r s
-------
r + s

which is probably d) but you left the parentheses out

Answer 2

yes