vcbabu wrote:

Q : N IS AN INTEGER FROM 1 TO 99 INCLUSIVVE WHAT IS THE PROB THAT N(N+1) IS DIVISIBLE BY 3 ?

if n = 1, n(n+1) = 1x2 ...... not divisible.

if n = 2, n(n+1) = 2x3 ...... divisible.

if n = 3, n(n+1) = 3x4 ...... divisible.

if n = 4, n(n+1) = 4x5 ...... not divisible.

if n = 5, n(n+1) = 5x6 ...... divisible.

if n = 6, n(n+1) = 6x7 ..... divisible.

if n = 7, n(n+1) = 7x8 ...... not divisible.

so on.

the pattren is 2 out of 3 is divisible by 3. so the prob = 2/3 or 66.67%.

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