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.
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)”
Not a bad approach, but 100/150 is 0.6666, not 0.75.