Sally and Lucy are running in the marathon. Sally runs at 7 mph and Lucy runs at 5 mph. If they start at the same time, how long will it be before they are 1/2 mile apart?
7x-5x=1/2
x=1/4 hour; 15 minutes
My question is why do you subtract 7x-5x and not add? My theory is that the miles apart is under 1 mph.
Also, is there a way to know when to add or subtract?
Thanks in advance.
7x-5x=1/2
x=1/4 hour; 15 minutes
My question is why do you subtract 7x-5x and not add? My theory is that the miles apart is under 1 mph.
Also, is there a way to know when to add or subtract?
Thanks in advance.