Question

The water level in an inflatable pool decreases by about 6.35×10−16.35×10−1 centimeters each day due to evaporation. There are 8.64×1048.64×104 seconds in a day. About how many centimeters does the water level in the pool decrease each second? Drag and drop the values to the boxes to express the answer in scientific notation. PLZ HELP!!!

Answer 1

The answer is "7.3 x 10⁻⁶ cm".

water level in pool decreases each day by = 6.35 x 10⁻¹ cm
Seconds in one day = 8.64 x 10⁴
water level decreases each second = ?
In 8.64 x 10⁴ seconds water level decreases by 6.35 x 10⁻¹ cm
So, in one second water level decreases by =  6.35 x 10⁻¹ cm / 8.64 x 10⁴ 
= 0.635 / 86400
=0.0000073495
=0.0000073
=7.3 x 10⁻⁶ cm

Answer 2

7.35x10^-6 cm/sec  
This looks like an exercise in dividing numbers in scientific notation. So let's do it.  
6.35x10^-1 / 8.64x10^4 
 In order to divide, first divide the significands as you would any decimal. 6.35 / 8.64 = 0.734953704 
 Then subtract the exponents:
 -1 - 4 = -5 
 So your result is
 0.734953704x10^-5 
 But your new significand is not in the range [1, 10). It's too small. So multiply it by 10 to shift the decimal 1 place to the right and subtract 1 from the exponent to compensate. So
 7.34953704x10^-6 
 Finally, round the result to the same number of significant digits as your least accurate piece of data which is 3 digits. So the final answer is 7.35x10^-6 cm/sec.