This morning I took my three children to an internet cafe. Jay used the internet for 37 minutes and was charged $17.40, whilst Kay's 56 minutes cost $20.25, and Harry had to pay $19.05 for the 48 minutes that he spent online. Which of the following formulae does this cafe use to charge for its internet facilities?

Explanation

To determine which formula the cafe uses to charge for its internet facilities, we can analyze the given information.Let's consider Jay's charges:Jay used the internet for 37 minutes and was charged $17.40.If we assume the formula for Jay's charges is A + (B x no. of minutes), we can set up an equation:$17.40 = A + 37BNow, let's consider Kay's charges:Kay used the internet for 56 minutes and was charged $20.25.If we assume the formula for Kay's charges is A + (B x no. of minutes), we can set up an equation:$20.25= A + 56BNext, let's consider Harry's charges:Harry used the internet for 48 minutes and was charged $19.05.If we assume the formula for Harry's charges is A + (B x no. of minutes), we can set up an equation:$19.05 = A + 48BBy solving any two of these equations simultaneously, we can find A (the fixed charge for access to internet) and B (the charge per minute).Subtracting Harry's equation from Kay's equation:$20.25 - $19.05 = 56B - 48B$1.2 = 8BB = $1.2/8B = $0.15Now we can substitute the value of B into any equation and solve it for A.Using Jay's equation:$17.40 = A + 37($0.15)$17.40 = A + $5.55A = $17.40 - $5.55 A = $11.85Based on the calculations, A (the fixed charge for access to internet) is $11.85, and B (the charge per minute) is $0.15. Hence, the correct formula for the cafe's internet charges is option D) $11.85 + $0.15 per minute.