Both
1 times a=a
and
b times 0=0
When multiplying exponents, remember the first rule: when multiplying similar bases, add powers together. 52% + 56% =? The bases of the equation remain unchanged, while the exponents' values are added together. Adding the exponents is only a quick way to get at the answer. Simply add the exponents to multiply exponential expressions with the same base. Simplify. The product rule applies because the base of both exponents is a. With a common basis, add the exponents.
Answer would be C.
Why A would be incorrect: 100m^2 is 100m × 100 m. That would be as big as a football field.
Why B would be incorrect: 1cm^2 is 1cm × 1cm. You can use a regular 15 cm to measure a piece of paper with the length of 1cm each side.
Why C would be correct: 1m^2 = 1m × 1m and it is also equals to 60cm × 60 cm. A 1 meter ruler = 60 cm = 4 times of your average 15 cm ruler. So, it is reasonable that a classroom is 10m by 10m in length and breadth.
Why D would be incorrect: The same explanation applies to here as well. Things that can be measured with 1m × 1m is a square table so your classroom can't be that small to fit an average of 30 to 40 students in there.
I hope my explanations were detailed and easy to understand. :)
Answer: A. 85.7
Step-by-step explanation:
Given : Two sections of a class took the same quiz.
Section A had 15 students who had a mean score of 80, and Section B had 20 students who had a mean score of 90.
We know that , 
Then , for section A :
Similarly in Section B, 
Total scores = Sum of scores in sec A+Sum of scores in sec B
=1200+1800=3000
Total students = Students in sec A +Students in sec B
=15+20=35
Now , the mean score for all of the students on the quiz =
Hence, the approximate mean score for all of the students on the quiz = 85.7
Thus , the correct answer is option A. 85.7.
