Start learning 50% faster. Sign in now
15 years ago, Average age of 80 teachers = 50 years 8 years ago (just before retirement of Principal), Average age of 80 teachers = 50 + 7 = 57 years And the same time total age of 80 teachers = 80 × 57 = 4560 years And the total age of remaining 79 teachers when just the principal has retired = 4560 – 60 = 4500 years 1 year later (i.e, 7 years ago from present) Total age of 79 teachers (just before the recruitment of new Principal) = 4500 + (1 × 79) = 4579 years And the total age of 80 teachers including new principal just after the recruitment = 4579 + 56 = 4635 years Thus, the present age of all 80 Teachers = 4635 + (7 × 80) = 5195 years ∴ Present average age of all the 80 Teachers = 5195/80 years. Alternate method: Let the present average age of all teachers be X The sum of the age of all the teachers 15 years ago = 80 × 50 = 4000 years 8 years ago the sum of the age of the teachers = 4000 + (7 × 80) - 60 = 4000 + 560 - 60 = 4500 years When new principle is recruited then age of the teachers = 4500 + (79 × 1) + 56 = 4500 + 79 + 56 = 4635 years The sum of the age of the teachers at present = 4635 + (7 × 80) = 4635 + 560 = 5195 years The present average age of all the teachers = 5195/80
A contractor hires 12 workers to complete a project in 20 days. After 8 days, 4 more workers are employed, and the project is completed 2 days earlier. ...
A, B and C can do a work in 8, 16 and 24 days respectively. They all begin together. A continues to work till it is finished, C leaving off 2 days and B...
A trip from Mumbai to Pune takes 4 hours 30 minutes at a speed of 60 km/hr. How long (in hours) will it take to complete, if the speed is 15m/sec?
Working alone, B can complete the work in 20 days. C is twice as efficient as B and A takes 2 days more than it takes C to complete the work. Working to...
If 10 men can complete a piece of work in 12 days by working 7 hours a day, then in how many days can 14 men do the same work by working 6 hours a day?
'K' can do 3/4th of a work in 6 days and 'J' can do 2/5th of the same work in 4 days. How long (in days) will they take, if they w...
A and B can do a certain work in 6 hours, and A, B and C together take 4 hours to do the same. How long will it take for C alone to accomplish the task?
A and B can complete a work together in 36 days. If A alone can complete one-fourth of the work in ‘x’ days and remaining work is completed ...
Girish can paint a picture in 4 days when he works for 8 hours per day. Due to illness, he could work for only 6 hours per day and was required to finis...