Question

A girl rides a bicycle with a speed of 10 km/h for 2 hours
and 15 km/h for next 3 hours. Find the distance moved by
her and average speed.

Answer 1

GIVEN :

• A girl rides a bicycle with a speed of 10 km/hr for 2 hours and 15 km for next 3 hours.

TO FIND :

• The distance moved by her = ?
• Average speed = ?

FORMULAS USED :

• Distance = speed × time.
• Average speed = total distance/time.

SOLUTION :

CASE I :

We are given,

• Speed = 10 km

• time, t = 2 hours

Now, to find the distance = ?

We know that,

$\sf \implies Speed \ = \ \dfrac {distance}{time}$

$\sf \implies Distance \ = \ Speed \times time$

Put the given values in the above formula,

$\implies \sf Distance \ = \ 10 \ × \ 2$

$\qquad \large {\boxed {\sf Distance \ = \ 20 km}}$

CASE II :

We are given,

• Speed = 15 km/hr

• time, t = 3 hours

Now, to find the distance = ?

$\sf \implies Distance \ = \ Speed \times time$

Put the given values in the above formula,

$\implies \sf Distance \ = \ 15 \times 3$

$\qquad \large {\boxed {\sf Distance \ = \ 45 \ km}}$

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To find the average speed = ?

We know that, $\sf Avg \ speed \ = \ \dfrac {total \ distance}{time}$

Total distance = 20 + 45 = 65 km.

$\implies \sf Avg \ speed \ = \ \dfrac {65}{5}$

$\qquad \large {\boxed {\sf Avg \ speed \ = \ 13 \ km/hr}}$

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Answer 2

Given :

• A girl rides a bicycle with a speed of 10 km/h for 2 hours and 15 km/h for next 3 hours.

To Find :

• The distance moved by her = ?
• Average speed = ?

Solution :

⚬ Case (I) ⚬

• Speed = 10 km/hr
• Time taken = 2 hours
• Distance = ?

★ Finding the distance for first 10 km/hr :

→ Distance = Speed × time

→ Distance = 10 × 2

→ Distance = 20 km

• Hence,the distance covered by bicycle for first 10 km/hr is 20 km.

⚬ Case (II) ⚬

• Speed = 15 km/hr
• Time taken = 3 hours
• Distance = ?

★ Finding distance for next 15 km/hr :

⟶ Distance = Speed × time

⟶ Distance = 15 × 3

⟶ Distance = 45 km

• Hence,the distance covered by bicycle for next 15 km/hr is 45 km.

★ Total distance covered by the bicycle :

➻ Total distance = distance covered by the bicycle for first 10 km/hr + distance covered by the bicycle for next 15 km/hr

➻ Total distance = 20 km + 45 km

➻ Total distance = 65 km

• Hence,total time distance covered by the bicycle is 65 km.

★ Total time taken by the bicycle :

➺ Total time taken = Time taken by the bicycle for first 10 km/hr + Time taken by the bicycle for next 15 km/hr

➺ Total time taken = 2 hours + 3 hours

➺ Total time taken = 5 hours

• Hence,the total time taken by the bicycle is 5 hours.

★ Now, let's find the average speed of the bicycle :

➝ Average Speed = Total distance travelled ÷ Total time taken

➝ Average Speed = 65 ÷ 5

➝ Average Speed = 13 km/hr

• Hence,the average speed of the bicycle is 13 km/hr.