Question

the average of three numbers is 6.if two of the numbers are 6 and 7 ,the third number is

Answer 1

let third number is x
avg. = total sum / total number
total sum = 6+7+ x
total number = 3
then 6+7+ x /3 = 6
13+ x = 18
x = 5

Answer 2

(1) Distance travelled in first 5 sec= area of ABDE= 20×s=80m

(2) Distance travelled after the brakes are applied (area of BCD)=

2

1

×8×5=20m

(3) Total distance travelled= AreaofABCDE+AreaofBCD=80+20=100m

(4) Acceleration during the first 5 sec= 0, because uniform velocity.

(5) Acceleration during the last 8 sec= v=0,u=20m/s,t=8sec

⇒v=u+at⇒0=20+a(8)

⇒a=−2.5m/s

2