LostinNY wrote:
(1) On Tuesday it took Bill 15 minutes longer to drive from home to school than on Monday. So, 1.5t=t+15. Solving for t gives: t=30 minutes. Sufficient.
I understand the equation set up, but how do you deduce for t in this case? Subtract t from both sides of the equation > .5t = 15 ….how do you get t = 30?
LostinNY - I hope your GMAT™ experience is finished by now, but I will respond to your question in hopes that someone else who may be experiencing a similar mental block might be able to push past it. Keep in mind, .5t = 15 is the same as 1/2t = 30. You might have been thinking that 15 divided by a half is 7.5--I know I have seen others in my tutoring sessions who have followed such a line of thought. However, it is 15 divided by 2 that equals 7.5. When you divide by a half, you double the quantity instead. If you think of the equation as a fraction instead and solve for
t algebraically, then the correct line emerges:
1/2
t = 15
(2)(1/2)
t = (2)(15) (multiply both sides by 2 to cancel out the fraction on the left-hand side)
(1)
t = (30)
t = 30
I hope that helps.
578vishnu wrote:
Hi !
I could not finish this question because ran out of time. Otherwise, its an easy one.
However, I'm unnecessarily getting confused over this part - On Tuesday it took Bill 1.5 times as long
Does it mean -
if Bill usually takes "t"
Then on Tuesday it took him "t+1.5t" or "1.5t" ?
as long is confusing me!
578vishnu, "1.5 times as long" means just that, that it takes an equal amount of time--in this case,
t--plus another half of that amount of time, or 0.5
t. If you break down the problem the way you outlined, then, translated, you are saying "just as long as... and then another one and a half times the original amount of time." I think you will agree that that wording is much more confusing! Mathematically, of course,
t + 1.5
t = 2.5
t. If you want to think of the decimal as a percent, 2.5 would be 250%, rather than the desired 150%, or one and a half times greater. If the question had said the amount of time had
increased by 1.5 times and asked about the total time instead, then the increase would indeed be 1.5
t, and your original interpretation would be correct. I could see such trickery appearing in a GMAT™ question. Good luck with your studies.