Maths
posted by Magana .
The 3rd term of an AP is 10 more than the first term while the fifth term is 15 more than the second term.find the sum of the 8th and 15 term of AP.if the 7th term is seven times the first term.

a saturated solution of salt X contain0.28g of the salt in 100cm3 of solution at 25degree centigrate, what is the solubility of the salt X at this temperature (R.m.m of X=56)

Let the 1st term be "a" and the 2nd term be "a+d" then 3rd term = a+2d = 10+a(i.e 10 more than the 1st term) and 5th term = 15+a+d(i.e 15 more than the 2nd term). Then 2d = 10(from 1st statement). This implies that d =5. Then the 7th term = a+6d =7a(7 times the 1st term). 6a = 6d =6(5) =30. Hence, a =30/6 = 5. Also, 8th term = a+7d =5+7(5) = 40 and 15th term = a+14d = 5+14(5) = 75. Finally their sum is 40+75 = 115. Thanks