is 13% the answer?
let m be the rate per month , then 1.15m is the rate per month after increase
let d be the number of days he used garage, then total cost assuming 30 days in month = md/30
let n be days to be reduced to remain at same cost, so we get
we need to find n*100/d
md/30 = 1.15m (d-n)/30
==>
d = 1.15(d-n)
divide both sides by d ==>
1 = 1.15 - 1.15n/d
==>1.15n/d = .15
==>100n/d = 15/1.15 = 13
_________________
Thanks, Sri
-------------------------------
keep uppp...ing the tempo...
Press +1 Kudos, if you think my post gave u a tiny tip