₦airaland Forum

You've almost nailed a job and then the interviewer placed on your table a white paper containing the following...

Legend has it that the inventor of the game called chess was told to name his own reward. His reply was along this lines.

Imagine a chess board.

Suppose one grain of corn is placed on the first square.
2 grains on the second
4 grains on the third,
8 grains on the fourth,

and so on until you get to the 64th square.

I would like as many grains of corn as the chess board now carries.

We were given just 5 minutes to do this...

And at the end, they will offer you 40k

Some employers sha

Emmaesty:
And at the end, they will offer you 40k

Some employers sha

40k? This is not one of those jobs.

This is a geometric progression (g.p) with ratio = 2, a = 1 (first number) and n = 64.
we use formula for sum of a geometric progression which is s = a(1-r^n)/1-r


After substituting the values, Final answer has to be in standard form if calculators are not allowed
Something like 2^64 - 1 or even just 2^64

I dont even understand

Ifeshyne:
This is a geometric progression (g.p) with ratio = 2, a = 1 (first number) and n = 64.
we use formula for sum of a geometric progression which is s = a(1-r^n)/1-r


After substituting the values, Final answer has to be in standard form if calculators are not allowed
Something like 2^64 - 1 or even just 2^64

U go school.... This is simply application of what u learnt in school in a real life situation.

128 coins

Ifeshyne:
This is a geometric progression (g.p) with ratio = 2, a = 1 (first number) and n = 64.
we use formula for sum of a geometric progression which is s = a(1-r^n)/1-r


After substituting the values, Final answer has to be in standard form if calculators are not allowed
Something like 2^64 - 1 or even just 2^64

Your head is soo in there.

OP...give her the job sharperly

Ifeshyne:
This is a geometric progression (g.p) with ratio = 2, a = 1 (first number) and n = 64.
we use formula for sum of a geometric progression which is s = a(1-r^n)/1-r


After substituting the values, Final answer has to be in standard form if calculators are not allowed
Something like 2^64 - 1 or even just 2^64

ds chick deserves d job, not d o.p

All you should have done is raise 2 to a power of 63 judging by the trend set with the information given

Brilliant Minds ...

agrovick:
All you should have done is raise 2 to a power of 63 judging by the trend set with the information given

you are wrong.. It is (2^64) - 1 which is different from 2^(64-1)

my answer;
you definitely need a formula.. This is a GP series of the form 1, 2, 4, 8, 16, 32,...

From the above,
first term, a = 1, common ratio, r = 2,
supply this in the formula of sum of nth term of a GP..
S_n = a(rⁿ - 1)/(r-1) since r > 1

therefore, S₆₄ = 1(2⁶⁴ - 1)/(2-1),
S₆₄ = 2⁶⁴ - 1

There's nothing wrong about it. 2 to the power of 63 is correct and you don't need any formula to get this solved

dejt4u:
you are wrong.. It is (2^64) - 1 which is different from 2^(64-1)

Na wa ohhh..i hate calculations ehhhh.....

H2Ossss:
U go school.... This is simply application of what u learnt in school in a real life situation.

Lool, hi!

Ifeshyne:
This is a geometric progression (g.p) with ratio = 2, a = 1 (first number) and n = 64.
we use formula for sum of a geometric progression which is s = a(1-r^n)/1-r


After substituting the values, Final answer has to be in standard form if calculators are not allowed
Something like 2^64 - 1 or even just 2^64

Nice one,but hope u knw that 2「63 is not the final answer,since the person said d whole grains which d board can carry....it means that,u gonna add all d grains from the 1st box-the 64th box....mind u 2「63,is the total numbers of grains on the 64th box....they want u to add up from 2「0 through 2「63....
Which is pure madness,i will tell them that i dont want to imagine again.

dejt4u:
you are wrong.. It is (2^64) - 1 which is different from 2^(64-1)

Let me break it down a bit, 2 is the common factor (don't ask me how, I only took an informed guess)
1st square = 2^1-1 = 2^0 = 1
2nd square= 2^2-1 = 2^1 = 2
3rd square = 2^3-1 = 2^2 = 4
4th square = 2^4-1 = 2^3 = 8
64th = 2^64-1 = 2^63

LastMumu:
What's with the whole interest in corns and grains? If I were you, I would have asked the recruiter if he was a fowl in his previous life.

Rotfl! You are one nairalander I will love to meet in person

agrovick:
Let me break it down a bit, 2 is the common factor (don't ask me how, I only took an informed guess)
1st square = 2^1-1 = 2^0 = 1
2nd square= 2^2-1 = 2^1 = 2
3rd square = 2^3-1 = 2^2 = 4
4th square = 2^4-1 = 2^3 = 8
64th = 2^64-1 = 2^63


Rotfl! You are one nairalander I will love to meet in person

Now they want u to addup from 2「1-1 through 2「64-1
Which is The total number of grains which the board can carry.

tompat86:
Now they want u to addup from 2「1-1 through 2「64-1 Which is The total number of grains which the board can carry.

You are right, I missed that part. Will this format be correct
2^0 + 2^1 + 2^2 + 2^3... +2^63

agrovick:
You are right, I missed that part. Will this format be correct

2^0 + 2^1 + 2^2 + 2^3... +2^63

Yes Boss
And they expect u to solve it in 5mins,for a 30k job...