If sum of n terms is given by Sn = 3n2 + 5n, then the common difference of this AP is:
We know S1is the sum of 1st term which is a
S1 = 3 + 5 = 8 = a
S2 is sum of first two terms
S2=3 * 4 + 5 * 2 = 12 + 10 = 22
And We have a2= S2 - S1 = 22 - 8 = 14
d = a2 -a1 = 14 - 8 = 6
What is the sum of the first 50 multiples of 3?
An athlete wants to improve his stamina, so he decides to increase the distance he runs by half a kilometer every day. If he starts with 5 km on first day, find how much he runs on the 10 th day
Distance increased every day is the common difference for the AP which is 0.5
Initial distance is 5 km , so a=5
To find the distance at 10th day, so n=10
A tree in each year grows 4cm less than it grew in previous year. If it grew 1 metre in the first year, in how many years will it have ceased growing and what will be its height then,
One metre = 100 cm, a = 100 cm
since every year it grows 4 cm less than it did the preceding year, d = -4
Thus, it is an AP, with initial term a = 100 and d = -4
The tree will stop its growth, when nth term of the series is 0.
Nth term = a + (n - 1)d
0 = 100 + (n - 1)(-4)
0 = 100 - 4n + 4
0 = 104 -4n
4n = 104
n = 104/4
n = 26 years
If Ss = 32, S4 = 28 ~~ What is ts =?
How many terms are there in 20, 25, 30......... 140
Which term of the A.P 10,8,6,… will be the first negative term?
Find the sum of first 40 integers divisible by 6
During the festival season , a girl wants to prepare a design at the entrance to her house. The pattern is such that starting with one dot she wants to go on increasing the number of dots by 3 every time. In which row will she have 55 dots?
Find the fifth term of an A.P whose first term is -1 and common difference is -3