Hi,

I found online a nice (and seemed easy) math problem.

Rocket A travel from Mars to Earth in 200 days
Rocket B travel from Earth to Mars in 150 days, but take off 30 days later

When they cross each other, which one is the closet to the earth ?

So they give a “flat” answer, without giving any explanation on how they reach this conclusion.

What would be your simplest Mathematical solution for this ?

Thanks.

  • DerisionConsulting@lemmy.caEnglish
    0·
    2 months ago

    If I was explaining it to someone, I would get them to figure out the speed as a percentage of the journey.
    100/200 = 0.5 per day for A
    100/150 = 0.75 per day for B.

    Then, I would get them to figure out where A was when B starts the journey.
    30*0.5 = 15

    So, we care about 85% of the journey.

    What else do we know?
    We know that the ships get 1.25% of the total distance each day if they are leaving from opposite sides (0.5 + 0.75).

    So, that turns this into the question “How many days does it take to go 85 if you are going 1.25 per day? (85/1.25)”