Mangala started doing physical exercise 10 minutes for the first day. She will increase the time of exercise by 5 minutes per day, till she reaches 45 minutes. How many days are required to reach 45 minutes?

3. Mangala started doing physical exercise 10 minutes for the first day. She will increase the time of exercise by 5 minutes per day, till she reaches 45 minutes. How many days are required to reach 45 minutes?

Sol. Since the workout time Mangala increases by 5 minutes everyday after the first day, the successive workout times are in A.P.

Workout time for first day (a) = 10 minutes.

Increases in workout time (d) = 5 minutes

Let No. of days required to reach workout time of 45 minutes be ‘n’ days.

∴ tn = 45

tn = a + (n – 1) d

∴ 45 = 10 + (n – 1) 5

∴ 45 = 10 + 5n – 5

∴ 45 = 5 + 5n

∴ 45 – 5 = 5n

∴ 5n = 40

∴ n = ⁴⁰/₅

∴  n = 8

∴  8 days required to reach work out time of 45 minutes.