[ taken from: NMOS 2010 Olympiad Competition by NUSH ( Preliminary Round) ]
My solution:
. _______ ? ________
. / \
From Betty |--------------------|
To Cathy:
Case 1: $140 10% disc. / \ / \
. |--------------------|----|-------|
Case 2: $200 5% disc
. / \ / \
. |--------------------|--------|---|
10% - 5% = 5%
$200 - $140 = $60
5% --> $60
100% --> $60 x 100 / 5 = $1200
Cost of camera from Betty --> $1200 - $200 - $60 = $940
