Question

On Monday Carla runs 2 5/8 in 15 minutes

A.what is s average rate of speed in miles per hour ,for s run? Show your work or explain how you know.
On Tuesday Carla decides to jog instead of run and so decreases her average rate of speed by 20 percent
B.How many miles does carla Noh in 50 minuets on Tuesday? Show your work and explain how u know.

Answer 1

(A)

`v=(7)/(42240)mph`

(B)

`d=(7)/(63360)miles`

Explanation:

(A)

We are given

distance traveled is

`=2(5)/(8)= (8* 2+5)/(8)=(21)/(8)in`

we know that

1 inch =
`(1)/(12)feet`

We can multiply both sides by 21/8

`(21)/(8)in=(1)/(12)* (21)/(8) feet`

`(21)/(8)in=(7)/(32)feet`

so,

`d=(7)/(32)feet`

we know that

1 mile =5280 feet

`d=(7)/(32)*(1)/(5280) miles`

`d=(7)/(168960)mile`

time is 15 minutes

we know that

160 min =1 hour

so,

`15min=(15)/(60)hour`

`15min=(1)/(4)hour`

`t=(1)/(4)hour`

now, we can find speed

`v=(d)/(t)`

now, we can plug values

`v=((7)/(168960))/((1)/(4))`

now, we can simplify it

`v=(7)/(42240)mph`

(B)

On Tuesday Carla decides to jog instead of run and so decreases her average rate of speed by 20 percent

so, average speed becomes

`v=(7)/(42240)*(80)/(100) mph`

`v=(7)/(52800)mph`

We are given

time =50 min

now, we can find time in hour

`t=(50)/(60)hr= (5)/(6)hr`

we know that

distance = (velocity)*(time)

we get

`d=(7)/(52800)* (5)/(6)miles`

`d=(7)/(63360)miles`

Answer 2

(a) 10.5 miles/hour

(b) 6.5 miles

Explanation:

(a)

Carla runs
`2(5)/(8)=(21)/(8)`

time taken by Carla=15 minutes=15/60 hours.

Hence Average rate of speed = total distance/total time

=
`(21)/(8)*(60)/(15)\\\\=10.5`

Hence, the average rate of speed in miles per hour is 10.5 miles/hour.

(b)

on Tuesday Carla decides to jog instead of walk and decreases her speed by 20%(20/100=0.2).

so her speed=10.5-0.2×10.5

=8.4 miles/hour.

Now distance travelled by her in 50 minutes(50/60 hours)=8.4×(50/60) miles

=6.5 miles.