Stat1 : plant 2 less than estimated Total saplings planted-38
total time may be more than 380min or less than 380 mins because avg time is 10 min
A and D are incorect

Stat2 ;tonya planted within 15 sec of estimated time also prove that he will plant sapling within 380 mins. It can be above 380 min or it can be less than than 380
Option E is correct.
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So for each sapling 600 seconds are required.
Total time taken is 40*600 =24000 sec.
95% of 24000= 22,800 sec.
We need to know whether Tanya's time was within 22,800 sec. or not.

(1) The number of saplings that Tonya planted was 2 less than her estimate.
We do not know the time she took for each sapling, hence cannot figure out her total time. INSUFF.

(2) The average time that Tonya spent to plant each sapling was within 15 seconds of her estimated time per sapling.
We do not know the number of saplings she planted hence here also we cannot figure out her total time.

1+2

Number of saplings 38 and time within 15 sec. of her original time, hence

If she takes 14 seconds extra or 614 seconds for each sapling her total time = 614*38 =23,332, which is more than 95%
If she takes 14 seconds less or 586 seconds for each sapling her total time = 586*38=22,268, which is less than 95%
INSUFF.

Ans- E

Hope it's clear.
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VeritasKarishma Bunuel @Empowergmatrich MathRevolution Can you please help me understand this question. According to me the question asks whether Tonya completed the work within 380 minutes or not. So I think both sentences tells that at exactly 380 minutes she must have completed the work. Still I want your approach and explanation..

Krishchamp:

Work - plant saplings along the median of a highway
Question: Was the amount of time that it took her to complete the work no more than 95 percent of her estimated total time?

Estimations:
She will need 40 saplings and take 10 mins per sapling. So she will need 400 mins to complete the work.

95% of this time is 380 mins.
Question becomes: Was the amount of time that it took her to complete the work no more than 380 mins?

(1) The number of saplings that Tonya planted was 2 less than her estimate.

She actually needed only 38 saplings. But we don't know how much time she planted them in.

(2) The average time that Tonya spent to plant each sapling was within 15 seconds of her estimated time per sapling.

The avg time taken per sapling was somewhere between 9 mins 45 secs and 10 min 15 secs. We don't know how many saplings she planted.

Together,
We know she planted 38 saplings. Had she taken on average 10 mins per saplings, total time taken would have been 380 mins. But her average could have been 9 m 45 secs in which case she took less than 380 mins or her average could have been 10 m 15 secs in which case she took more than 380 mins. Do we know whether she took less than 380 mins or more? No. Not sufficient.

Answer (E)
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Statement 1:

The number of saplings planted were 38 which is equivalent to \(\frac{2}{40} = 5\)% decrease in the number of saplings planted.

But we have no information on the average amount of time taken to plant each sapling. If it is more than the estimated 10 minutes, then the total time would be more than 95%, and if less than 10 minutes, then less than 95%

Thus INSUFFICIENT.

Statement 2:

The saplings are planted within 15 seconds of the estimated time, i.e. between 9 min 45 sec and 10 min 15 secs.

However, no information available on the number of saplings planted.

Thus INSUFFICIENT.

Combine (1) & (2):

We know that the number of saplings reduced by 5%. Thus if the saplings were planted in 10 mins, the actual total time would be 95% of the estimated total time. Any increase or decrease in the actual average time for planting each sapling can increase or decrease the total time to more than 95% or less than 95% of the estimated time.

Thus INSUFFICIENT.

Answer (E)

NB: No hardcore calculations required once figure out that the number of saplings planted have reduced by 5%