Question

2481=(+-1+-2+-3???+-n) find the minimum value of n​

Answer 1

Answer:

n = 70

Step-by-step explanation:

2481=(+-1+-2+-3???+-n) find the minimum value of n​

2481 = ±1 ±2 ±3 ± ................±n

if We take only positive Values

1 + 2 + 3 + .............................+ n

Sum of first n Terms = n(n + 1)/2

n(n + 1)/2 ≥ 2481

=> n(n+1) ≥ 4962

70 * 71 = 4970 > 4962

Sum of 70 numbers = 2485   ( 4 above than 2481)

so 4 is extra , to reduce by 4 (we can take 2 as - instead of +)

if we take +2 as - 2 and all other terms positive

then sum would be exactly as required = 2481

n = 70

if we put Question like this

1 - 2 + 3 - 4 + ...........................................+ n

1 -2 = -1  3 -4 = -1 and so on

then for 2k Terms  sum would be - k

then last term should be 2k+1 such that sum 2481

=> -k + 2k + 1 = 2481

=> k = 2480

=> 2k = 4960

2k+1 = 4961

Last term = 4961

n = 4961