The first term of a geometric progression is twice its co...
The first term of a geometric progression is twice its common ratio. Find the sum of the first two terms of the G.P if its sum to infinity is 8.
8/5
8/3
72/25
56/9
Correct answer is C
Let the common ratio be r so that the first term is 2r.
Sum, s = a1−r
ie. 8 = 2r1−r
8(1-r) = 2r,
8 - 8r = 2r
8 = 2r + 8r
8 = 10r
r = 45.
where common ratio (r) = secondterm(n2)firstterm(a),
r = n22r
r = 45 and a = 2r or 85
45 * 85 = n2
3225 = n2
The sum of the first two terms = a + n2
= 85 + 3225
= 40+3225
= 7225
The total surface area of a hemispher is 75πcm2. Find the radius....
If y varies directly s the square root of (x + 1) and y = 6 when x = 3, find x when y = 9 ...
Evaluate without using tables (0.008) -13 x (0.16) - 32...
How many pupils took the test? ...
Find the remainder when 3x3 + 5x2 - 11x + 4 is divided by x + 3 ...