Given:
Three numbers in an AP, all positive.
Sum is 21.
Sum of squares is 155.
Common difference is positive.
We do not know what x and y stand for. Will just solve for the three numbers in the AP.
Let m=middle number, then since sum=21, m=21/3=7
Let d=common difference.
Sum of squares
(7-d)^2+7^2+(7+d)^2=155
Expand left-hand side
3*7^2-2d^2=155
d^2=(155-147)/2=4
d=+2 or -2
=+2 (common difference is positive)
Therefore the three numbers of the AP are
{7-2,7,7+2}, or
{5,7,9}
His conclusion wouldn't be valid because he didn't apply them on the same day. So, Brand A if applied first would be ahead of brand B which was applied 5 days later. Hope this helped!
The probability that both the chosen students are sophomores is 6/20 or 3/10 simplified.
the expresión that represents the probability that both students have chosen are sophomore is (6c1) (5c1) /(20c2)
When the concentration of a solution is expressed in weight percentages, that is just equal to the mass of solute over the mass of the total solution. For a solution weighing 210 grams, 5% of it is salt. That is equal to
210*0.05= 10.5 g salt
The rest of the amount, determined by difference, is the amount of solvent which is water.
water = 210-10.5 = 199.5 g salt
To solve for the new concentration, you add up 15 g to the already existing 10.5 g of salt in the solution. The water, on the other hand, remains constant.
Concentration = (15+10.5)/(210+15) = 0.1133 or 11.33%
