# Need math help **URL:** \ **Category:** Factual Questions\ **Created:** [September 8, 2017, 10:12pm UTC](https://boards.straightdope.com/t/need-math-help/795849 "2017-09-08T22:12:58Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![I.Dunno](https://avatars.discourse-cdn.com/v4/letter/i/9f8e36/32.png) [@I.Dunno](https://boards.straightdope.com/u/I.Dunno)\ **Post date:** [September 8, 2017, 10:12pm UTC](https://boards.straightdope.com/t/need-math-help/795849/1 "2017-09-08T22:12:58Z")
Recent Amtrak trip. Fares were different for trip out and trip back. Need help with allocating costs for return trip. Didn’t write it down at the time and Amtrak didn’t break it down on the ticket. (I DID write down the individual costs of the outbound ticket but as I said, it was a different fare.) Total came to $131.35. Now, whatever the original individual fare was, three seniors get 15 percent off and two children get 50 percent off. Is there some way, other than trial and error, to find the costs for the 5 tickets? (Three seniors will be the same each, and 2 child tickets will be the same each.) Any help is appreciated. Thanks. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [September 8, 2017, 10:16pm UTC](https://boards.straightdope.com/t/need-math-help/795849/2 "2017-09-08T22:16:21Z")
3 x 0.85x + 2 x 0.5x = 131.35 2.55x + x = 131.35 3.55x = 131.35 **x = 37.00** ---
**Author:** ![brad\_d](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@brad\_d](https://boards.straightdope.com/u/brad_d)\ **Post date:** [September 8, 2017, 10:21pm UTC](https://boards.straightdope.com/t/need-math-help/795849/3 "2017-09-08T22:21:31Z")
Solving this for x should work, I would think: 3 (0.85x) + 2 (0.5x) = 131.35 x would then be the base fare; senior and child tickets would be calculated by applying the discounts. Any un-discounted fees/taxes would screw this up a bit, but absent knowledge of them this may be the best we can do. Sent from my SM-G930V using Tapatalk ---
**Author:** ![I.Dunno](https://avatars.discourse-cdn.com/v4/letter/i/9f8e36/32.png) [@I.Dunno](https://boards.straightdope.com/u/I.Dunno)\ **Post date:** [September 8, 2017, 10:24pm UTC](https://boards.straightdope.com/t/need-math-help/795849/4 "2017-09-08T22:24:20Z")
That was FAST! Thanks Cooking! And thank you too Brad. 37 it is! ---
**Author:** ![brad\_d](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@brad\_d](https://boards.straightdope.com/u/brad_d)\ **Post date:** [September 8, 2017, 10:26pm UTC](https://boards.straightdope.com/t/need-math-help/795849/5 "2017-09-08T22:26:29Z")
Glad we could help. (Glad we agree on the approach, too!) Sent from my SM-G930V using Tapatalk ---
**Author:** ![I.Dunno](https://avatars.discourse-cdn.com/v4/letter/i/9f8e36/32.png) [@I.Dunno](https://boards.straightdope.com/u/I.Dunno)\ **Post date:** [September 8, 2017, 10:31pm UTC](https://boards.straightdope.com/t/need-math-help/795849/6 "2017-09-08T22:31:40Z")
> [@brad\_d](#): > > Glad we could help. (Glad we agree on the approach, too!) > > Sent from my SM-G930V using Tapatalk I was doing the math from CookingWithGas when your reply was posted. I can’t believe how fast the two answers came in. And I’ve been out of school a LONG time and am embarrassed to admit I should have known (and used to know) how to do this problem. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [September 8, 2017, 10:40pm UTC](https://boards.straightdope.com/t/need-math-help/795849/7 "2017-09-08T22:40:02Z")
4 minutes … not bad but we can do better I think …