Question

the percentage of tubes ,lifetime of which are greater than or equal to 900 hours(hint: 800-899 hrs= 62 tubes,900-999=48tubes,1000-1099=22 tubes)

Answer 1

We can write down the inequality as follows.

Let x be the number of tubes more than or equal 900hrs.

The maximum number of hrs is 1099.

Therefore :

900 ≤ x ≤ 1099

The value of x will be :

(900 - 999 =48) + (1000 - 1099 = 22) = 70

The total number of tubes :

70 + 62 = 132

70/132 × 100 = 53.03%