IQ test scores are normally distributed with a mean of 100 and a standard deviation of 15.find third quartile?

I don't have standard deviation tables in front of me, and this question would most easily be answered using the tables. 50% of the population has an IQ of 100 or below, so you are looking for the area under the bell curve where the next 25% of the population lies. You find this number in the tables, which will give you the number of standard deviations above the mean. Multiply the result times 15 and add it to 100. You are going to be less than 1 standard deviation away, so my estimate is somewhere around 110.