Number Theory

Number Bases

Number Bases: Level 4 Challenges


Let NN be the number that consists of 61 consecutive 3's, so N=333333613sN = \underbrace{333\ldots333}_{61 \, 3's}. Let MM be the number that consists of 62 consecutive 6's, so M=6666666626sM=\underbrace{6666\ldots666}_{62 \, 6's}. What is the digit sum of N×MN\times M?

Details and assumptions

The digit sum of a number is the sum of all its digits. For example the digit sum of 1123 is 1+1+2+3=71 + 1 + 2 + 3 = 7.

Let ff be a polynomial with nonnegative integer coefficients. If f(1)=7f(1)=7 and f(7)=7597f(7)=7597, what is f(10)?f(10)?

You have a weighing balance, which you can place weights on both sides of. You need to measure all weights between 1 and 1000.

For example if you have weights 1 and 3, you can measure test objects of weights 1, 3 or 4. You can also measure objects of weight 2, by placing 3 on one side and 1 on the side which contain the object to be weighed.

What is the minimum number of weights that you would need to be able to measure all (integral) weights from 1 kg to 1000 kg?

Calvin went to a newly discovered planet called "Pandora" to research their advancements in the field of Mathematics. He found the following equation scrawled in the dust:

3x225x+66=0x=4 or x=9\large{3x^2 - 25x + 66 = 0 \quad \Longrightarrow \quad x=4 \text{ or } x=9}

Can you help Calvin in finding the base, which is used in the Number System on Pandora?

Note: Symbols for digits in the Pandora System and Decimal system have the same value. e.g. 6 in Pandora represents six.

Find the number of integers that are between 11 and 100100 inclusive that when converted to binary have a digit sum of less than 5.5.


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