A car travels for 10 minutes at 30 km/h and then for
20 minutes at 45 km/h. What is the average speed for the whole journey

40 km/h

Step-by-step explanation:

s = ut where s - Distance

u - Speed

t - Time

when t = 10 min

= 10/60 hours

S1 = 30 * 10/60

= 5km

when t= 20 min

= 20/60 hours

S2 = 45 *20/60

= 15 km

Then total distance = S1 + S2

= 5 + 15

= 20 km

Total time period = (10 + 20 ) / 60 hours

= 1/2 hours

Then average speed = U

S = UT

U = S/ T

= 20/ 0.5 km/ h

= 40 km/ h

7! = 7×6×5×4×3×2

3! = 3× 2

as 7! is multiple of 3! because 7! contains 3! that is 3× 2 as factor

so 7! /(3! ) = 7× 6× 5× 4

= 42 × 20

= 840

its b) 840✌✌✌

dhruv⭐