Finding the contaminated pill jar.

There are 5 jars of pills. Each pill weighs 10 milli gram, except for contaminated pills contained in one jar, where each pill weighs 9 mg. You are given a scale, how could you tell which jar had the contaminated pills in just one measurement?

Answer: Take 1 pill from first jar, 2 from second jar, 3 from the third , 4 from fourth and 5 from fifth jar.
There are 15 pills and in ideal case there total weight should be 15*10 = 150 mg. Now that there is a jar with contaminated pill the weight is obviously less than 150 mg. If weight is 149mg then that means the jar 1 is contaminated. If weight is 148 mg then jar 2 is contaminated. If weight is 147 mg the jar 3 is contaminated. If weight is 146 mg then jar 4 is contaminated. If weight is 145 mg the jar 5 is contaminated.