If the cost of a telephone conversation varies directly as the length of the time of conversation, and if the cost of six minutes is $0.90, what would be the cost for a nine-minute call?

Question

Eli Assouline · Accepted Answer

Cost = #$1.35# As the cost is proportional to the time you can set up a direct proportion using equivalent fractions: #6/0.90 =9/x" "(larr "minutes")/(larr "cost")# #x = (9xx0.90)/6# #=1.35#

Julia Adams · Answer

Cost for a #9# minute call is #$1.35# Let length of time be #t# minutes and cost is #$c#, then, #c prop t or c = kt or k = c/t; k # is variation constant. # t= 6 , c =$0.90:. k = 0.90/6=0.15 # , therefore, variation equation is #c = 0.15 t ; t= 9 , c= ? c =0.15*9=$1.35# Cost for a #9# minute call is #$1.35# [Ans]

Eva Abramson · Answer

undefined To find the cost of a nine-minute call, we can use the concept of direct variation. Since the cost varies directly with the length of the conversation, we can set up a proportion:

6 minutes / $0.90 = 9 minutes / x

Solving for x:

x = (9 minutes * $0.90) / 6 minutes
x = $1.35

So, the cost for a nine-minute call would be $1.35.