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Andra travels 90 miles at an average speed of 70 mph.
She then travels a further 70 miles.
The average speed for the entire journey is 63 mph.
Assuming Andra didn't stop, what was her average speed for the final 70 miles to 2 dp?

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Andra Travels 90 Miles At An Average Speed Of 70 Mph She Then Travels A Further 70 Miles The Average Speed For The Entire Journey Is 63 Mph Assuming Andra Didnt class=

Sagot :

Answer:

54mph

Step-by-step explanation:

[tex] \textsf {\underline {To find :-}}[/tex]

The average speed at 2nd departure.

[tex] \textsf{ \underline {Given :-}}[/tex]

The speed during 90 miles travel = 70mph

The average speed during the entire journey = 63mph

The distance in second departure = 70 miles

[tex] \textsf {\large{ \underline{ Solution :-}}}[/tex]

The distance travelled in the entire journey

= 90 + 70 = 160 miles.

Then the time taken in entire journey will be

[tex] \sf \large = \frac{total \: distance}{average \: speed} \\ \\ \sf \large = \frac{160}{63} \\ \\ \sf \large = 2 \frac{37}{63}hours \\ \\ \sf \large = 2 \: hours \: 35 \: minutes[/tex]

Time taken at first departure

[tex] \sf \large = \frac{distance}{speed} \\ \\ \sf \large = \frac{9 \cancel0 }{7 \cancel0} \\ \\ \sf \large = 1 \frac{2}{7} \: hours \\ \\ \sf \large = 1 \: hour \: 17 \: minutes[/tex]

Time taken in second departure

= 2 hours 35 minutes - 1 hour 17 minutes

= 1 hour 18 minutes

Speed at second departure will be

[tex] = \sf \large \frac{distance}{time} \\ \\ \sf \large = \frac{70}{1 \frac{18}{60} } \\ \\ \sf \large = \frac{70}{1.3} \\ \\ \sf \large = 53.84 \: mph \\ \\ \sf \large = 54 \: mph[/tex]

The average speed at second departure was 54mph.