Question 10 of the 2011 Paper (1 Viewer)

[stattam]

10 (a)
The intensity I, measured in watt/m2, of a sound is given by I = 10–12 × e0.1L , where L is the loudness of the sound in decibels.
(i)
If the loudness of a sound at a concert is 110 decibels, find the intensity of the sound. Give your answer in scientific notation.
1
(ii)
Ear damage occurs if the intensity of a sound is greater than 8.1 × 10–9 watt/m2 . What is the maximum loudness of a sound so that no ear damage occurs?

The answers work out the answer as 89.996 which I understand but they round up their final to 90. Wouldn't 90 cause damage though as it is above the 89.996? I would have thought to round down to either 89.5 or 89. Would I be wrong?
Thanks

 

[ahdil33]

Hmm I remember this question from last year.

You never round down though if it's above .05

89.996 to one decimal place goes to 90, only thing that makes sense.

 

[stattam]

Yeah but then technically 90 would cause ear damage. You know?!?

 

[ahdil33]

Well yes technically. The only real correct answer is what you found. But for example if I needed to travel to the bus stop at 1.23 m/s to get there, and i rounded to 1.2, I technically wouldnt get there. but it dont matter, the point is you know the maths