Mrs kanja ,miss kanene and Mrs nyaga have to mark a form three contest for 160students .They take 5mins ,4mins and 12mins respectively to mark a script .If they all start to mark at 9.00am non-stop ,what is the shortest time they ca n take to complete the marking?

300 minutes

2:00 p.m

Step-by-step explanation:

Given the following:

Time taken to mark a script :

Mrs Kanja = 5mins

Miss Kanene = 4mins

Mrs Nyaga = 12 mins

Number of scripts = 160

Start time = 9:00 a.m

Rate at which each of them mark:

Mrs Kanja = t / 5

Miss Kanene = t/4

Mrs Nyaga = t/12

Combined rate :

t/5 + t/4 + t/12 = 160

(12t + 15t + 5t) / 60 = 160

32t / 60 = 160

32t = 160 * 60

32t = 9600

t = 9600 / 32

t = 300 minutes

300 minutes = 300/60 = 5hrs

9:00 a.m + 5 hours = 2:00 p.m