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 !

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

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.