The table shows some information about the lifetimes, t, in hours, of some lightbulbs. Lifetime Frequency
25 < t ≤ 50 76
50 < t ≤ 100 33
100 < t≤ 150 67
150 < t ≤ 200 28
200 < t ≤ 250 0
250 < t ≤ 300 82
300 < t≤ 350 36

Estimate the mean lifetime of a bulb.
Give your answer rounded to 2 DP.
Plz i need help with this answer quick plzzz

190.37 hrs.

Step-by-step explanation:

The mean lifetime will be the number of bulb•hrs divided by the number of bulbs.

t(avg) = 50(76) + 100(33) + 150(67) + 200(28) + 250(0) + 300(82) + 350(36)

                                 76 + 33 + 67 + 28 + 82 + 36

t(avg) = 61,300 / 322 = 190.372...

Rounding to two decimal places it ridiculous as the number of hours in each life band is different and have a range of up to fifty hours. We would get a different average time if we used the midpoint of each band as the lifetime and yet another average if we used the low end of the bands.

As the bands are most typically fifty hours wide and I chose to analyze the top end of each band, a reasonable engineering answer would be

140 ≤ t(avg) ≤ 190

the answer is d. 75%