Elementary Math Problem?
Jacob takes 3/4 h to fill one shelf at the supermarket. Henry can fill the shelves in half Jacob's time. There are 15 shelves. Henry and Jacob work together. How long will it take to fill the shelves? PLease explain how you did this.
Update:Thank you Michael! I'll give you top answer when I can.
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If Jacob fills a shelf in 45 minutes, and Henry does it twice as fast, that must mean that if jacob fills 1 shelf, then Henry could fill 2.
That means that they could fill 3 in 45 minutes.
3 times 5 is 15, so we would have to multiply 45 by 5 as well.
45*5=225
That is in minutes, so convert that to hours and minutes and you get 3 hours and 45 minutes.
If Jacob fills one shelf in 45 mins, and Henry does it in half the time, then Henry must be able to fill two shelves in 45 minutes. So if they work together, they'll be filling 3 shelves every 45 minutes. 15 divided by 3 = 5. it'll take 5 x 45 minutes to fill all 15 shelves. 5 x 45 minutes = 3 hours 45 minutes.
My perspective
J = 3/4 h/s or 4/3 shelf/hr
H = 3/8 h/s (1/2 the time) or 8/3 shelf/hr
Together = 12/3 shelves per hr = 4 shelves/hr or 0.25 hrs/shelf
0.25 hrs/shelf x 15 shelves = 3 3/4 hr
3/4 h + 3/8 h = 11/8 or 82 minutes and 30 seconds, 1 hr 22 minutes and 30 seconds. multiply that by 15, and get 1237.5 minutes, or 20.625 hrs.