Question

Justin rode his bicycle 3.7 miles a day for 20 days straight. How many miles did Justin ride altogether during the 20-day stretch?

Answer 1

distance = rate1*time1 + rate2*time2

 

Justin rode for t minutes at 10 mph, and for 30 minutes longer at 15 mph.  Since the rate is miles per HOUR, convert 30 minutes to 0.5 hours.  He rode t+ 0.5 at 15 mph.

 

25 miles = 15*(t+0.5) + 10*t

25 = 15t + 7.5 + 10t

17.5 = 25t

17.5/25 = t

0.7 hours = t  This is the time he rode at the slower rate (10 mph).  The time he rode at the faster rate is 0.7 + 0.5 = 1.2 hours

 

Check:

25 miles = 15*(t+0.5) + 10*t

25 = 15*(0.7+0.5) + 10*0.7

25 = 15*1.2 + 7

25 = 18 + 7

25 = 25

Check!
the numbers are changed but the formula is same
 

Answer 2

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Here is your answer.
Justin rode his bicycle 3.7 miles a day
Numbers of days are 20 days

Justin Ride altogether during the 20 days stretch. is
$= 3.7 \times 20 \\ = 74 \: miles$
Do Justin Ride 74 miles
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