Jasmine saves rupees 32 during the first month rupees 36 in second month and rupees 40 in 3rd month if we continue to save in this manner in how many month will see saved rupees 2000
Answers
Answered by
3
Using Arithmetic Progression
common difference = second term - first term
=36-32=4
Given,
S=2000 ,
a=32,
d=4,
n=?
Using the formula
S = n/2(2a+(n-1)d)
putting the values
2000 = n/2(2x32 + (n-1)4)
or, 4000 = n(64 + 4n - 4)
or, 4000 = 60n + 4n²
or, 4n² + 60n - 4000 = 0
or, n² + 15n - 1000 = 0
or, n² + (40 - 25)n - 1000 = 0
or, n² + 40n - 25n - 1000 = 0
or, n(n + 40) - 25(n + 40) = 0
or, (n-25)(n+40) = 0
therefore, n has to be either 25 or -40. As n cannot be in negetive so n has to be 25.
common difference = second term - first term
=36-32=4
Given,
S=2000 ,
a=32,
d=4,
n=?
Using the formula
S = n/2(2a+(n-1)d)
putting the values
2000 = n/2(2x32 + (n-1)4)
or, 4000 = n(64 + 4n - 4)
or, 4000 = 60n + 4n²
or, 4n² + 60n - 4000 = 0
or, n² + 15n - 1000 = 0
or, n² + (40 - 25)n - 1000 = 0
or, n² + 40n - 25n - 1000 = 0
or, n(n + 40) - 25(n + 40) = 0
or, (n-25)(n+40) = 0
therefore, n has to be either 25 or -40. As n cannot be in negetive so n has to be 25.
Similar questions