3 piles of 9 pictures is 27. Because 9*3=27. So, your answer should say "Alise had 27 pictures in all because 9*3=27"
Say x is the number
7x +3 = 39 -2x
Add 2x to each side
9x +3 =39
Subtract 3 from each side
9x =36
Divide by 9 on each side
x=4
Hope this helped
454=450
289=290
2,964=2,960
4 or less then let it rest 5 or more then let it soar is a helpful ryhme for rounding.
Let's figure this out as though we have no idea what the answer would be.
Step One
Find the new five numbers.
3*3, 8*3, 12*3, 17*3, 25*3
9 , 24 , 36, 51, 75
Step 2
Find the average
(9 + 24 + 36 + 51 + 75)/5 = 195/5 = 39
Step 3
Subtract the individual numbers from the average
(39 - 9) = 30
(39 -24) = 15
(39 - 36) = 3
(39 - 51) = - 12
(39 - 75) = -36
Step 4
Square the results from Step 3
30^2 = 900
15^2 = 225
3^2 = 9
(-12)^2 = 144
(-36)^2 = 1296
Step 5
Take the average of the results from step 4
(900 + 225 + 9 + 144 + 1296)/5
2574 / 5 = 514.8
Step 6
Take the square root of the result from step 5
deviation = sqrt(514.8)
deviation = 22.689
Step seven
Compare the two standard deviations.
s2/s1 = 22.689 / 7.563 = 3
Conclusion
If you are given 1 set of numbers to find a population standard deviation and you multiply each member by a, then the result will be a * the standard population deviation of the first set of numbers.
Note
Your calculator will do this as well, but you have to know how to enter the data into your calculator. That requires that you follow the directions carefully.
