Guessing game!

Number Theory Level pending

One day, Rashed and Rimi, two friends who claim to be best friends forever desire to spend some time in peace somewhere away from the busyness of the world. Rashed suggests the local park to be the perfect choice for them. Rimi agrees with his opinion and, so they go there and sit on a bench nearby a lake in the park, appreciating the tranquillity and natural beauty of their surrounding.

Rimi suddenly brings up the topic of birthday celebration. Together they discuss what an ideal birthday celebration will be like. Rimi secretly plans on arranging a surprise birthday party for Rashed. At the end of their discussion, she asks Rashed his birthdate.

Rashed, however, refuses to tell his birthdate. He tells her to guess it. He gives Rimi some clues that will aid her in guessing his birthdate.

The clues are following-

Both values of the day and month of Rashed’s birth date are cubic numbers .

These two numbers add up to 35 .

His year of birth is 1996 .

Rimi is not confident that she can solve this problem all by herself. Therefore, she requests your help as you happen to be a very dear friend of her. Now, it's your job to solve the problem.

For clarification: Type your answer in this form - MD1996. Suppose- Month is 12, Day is 23. Then, the answer will be typed as- 12231996. Remember: the answer must contain 8 digits. No more, no less! If any or both of the day or month values are single digit, you should put a '0' in front. Hope you get it!


The answer is 8271996.

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2 solutions

Define the following variables:

Rashed's month of birth is m m .

His day of birth is d d .

Value range of the variables:

d ( 1 ; 2 ; 3 ; 31 ) d∈(1;2;3; \cdots 31)

m ( 1 ; 2 ; 3 ; 12 ) m∈(1;2;3; \cdots 12)

Solving the problem:

Now we make use of the clues to find the exact value of the variables. The first clue tells us that m m and d d are cubic numbers. For better understanding,

m = x 3 m=x^3

d = y 3 d=y^3

Here, x x and y y are random variables and do not bear any significance in solving this problem.

Cubic numbers : 1 = 1 3 1=1^3 , 8 = 2 3 8=2^3 , 27 = 3 3 27=3^3 , 64 = 4 3 64=4^3 , 125 = 5 3 125=5^3 and so on...

1 , 8 , 27 , 64 , 125

We limit the range of possibilities upto the 3rd term of this geometric sequence, as further terms exceed the value range. So, m m can be either 1 or 8. d d can be anyone of the three: 1, 8, 27.

The second clue tells us that the sum of m m and d d is 35 35 . This gives us the equation: m + d = 35 m+d=35 . Replace the variables with any of the values from the set of possibilities . Try picking randomly from the set of possibilities ​ and see which values fit into this equation.

Possible replacements:

1 + 8 35 1+8\neq35

8 + 27 = 35 8+27=35

We see that the first replacement is a wrong one as it does not meet the condition (m plus d must be equal to 35). However, the second replacement values fit perfectly into the equation and HURRAY! We have found out the values of the variables.

From this experiment, we can conclude that 8 8 and 27 27 are values of m m and d d , respectively.

Therefore, Rashed's birthdate is : 27 27 / 08 08 / 1996 1996 ( sequence D/M/Y )

The answer to be typed is : 08271996 \boxed{08271996}

I am very sure you accidently swapped day and month - please that :)

Lukas Henke - 4 years, 11 months ago

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*check that

Lukas Henke - 4 years, 11 months ago

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I did, thank you for your concern. Please check my solution carefully, as well as the question. You had submitted a report earlIer and I had edited the question then.

Soha Farhin Pine Pine - 4 years, 11 months ago
Lukas Henke
Jul 10, 2016

The date contains d d (for day) and m m (for month). The relation can be written as d + m = 35 ; d , m i n t e g e r c u b e s d+m=35; d,m \in integer cubes If we take a look at the first few cube numbers, 1 3 = 1 1^3=1 , 2 3 = 8 2^3=8 , 3 3 = 27 3^3=27 and 4 3 = 64 4^3=64 , can see that d + m = 35 < 4 3 d + m = 35 < 4^3 . Therefore d , m ( 1 ; 8 ; 27 ) d,m \in (1;8;27) , which easily leads to 8 + 27 = 35 8+27=35 . Because m m can be at most 12 12 , it can only be 8 and 27 is left over for d d . The right solution is in the form D D M M 1996 DDMM1996 , which concludes to 27081996 \boxed{27081996}

please see the question. You ought to read the question with greater attention,

Soha Farhin Pine Pine - 4 years, 11 months ago

Your solution is incorrect

Soha Farhin Pine Pine - 4 years, 11 months ago

d,m(1, 8, 27) is incorrect. d(1, 8, 27) and m(1, 8)

Soha Farhin Pine Pine - 4 years, 11 months ago

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