A glass timer is made of two cones placed tip to tip on top of each other. The sand in the timer funnels down at a rate of 45mm. As the sand begins to fall, the depth of the sand is 3cm and the diameter of the top of the cone is 1.6cm. How much time does the timer measure.

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.