Decimal to Binary Help

Hello everyone,

I was watching the CBT Nuggets for 291. And I've heard people say the test only has the standard calculator. So, I am trying to do all this by paper. But, I dont understand when doing subnet masks and finding the number of bits required for the host after borrowing, he said go back to the orginal problem which says minimum subnet hosts required: 4,900 and he said to add 1 to this so it would be 4,900. Then he said convert this to binary, he did it with a scientific calculator, but I want to know how to convert 4,901 by hand into binary. I only the 128 64 32 16 8 4 2 1 and with all 1's would equal 255. But how do you do such a large number like 4901? I need to convert to binary this so I know how many bits the host will have, and by paper not scientific calculator.

Thanks for the help,

win2k8

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Paperclip

Basically by division.

4901/2 = 2450 remainder 1
2450/2 = 1225 remainder 0
1225/2 = 612 remainder 1
612/2 = 306 remainder 0
306/2 = 153 remainder 0
153/2 = 76 remainder 1
76/2 = 38 remainder 0
38/2 = 19 remainder 0
19/2 = 9 remainder 1
9/2 = 4 remainder 1
4/2 = 2 remainder 0
2/2 = 1 remainder 0
1/2 = 0 remainder 1

We continue dividing by 2 all the way until we reach 0, and then read the remainder digits from the bottom up.

1001100100101 is 4901 expressed in binary.

win2k8

Thank you for that advice. I noticed in the basic calculator a pattern:

if it ends with a .5 when you divide by 2 it is equivilant to having a remainder which means its 1

If it does not end with a .5 it has no remainder so it is 0.

Since their can be only 2 outcomes either a 0 or 1.

Thanks again,

win2k8

Paperclip

Exactly. When dividing by 2 with a calculator, anything ending in .5 you should remove the .5 and write down the whole number with a remainder of 1.

When dividing in your head or with long division on paper, you can just stop when you reach no decimal places and write down the whole number with a remainder of 1, rather than continue dividing the last 1 to get .5

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win2k8 wrote: »

Hello everyone,

I was watching the CBT Nuggets for 291. And I've heard people say the test only has the standard calculator. I need to convert to binary this so I know how many bits the host will have, and by paper not scientific calculator.

Thanks for the help,

win2k8

Its wise to know how to work it out manually but the "scientific calculator" was there on both my visits to the 291. As it happened there weren't may IP questions on my tests.

Paperclip

I thought I recalled it was there in the NT4 and 2000 exams, but it was a long time ago and I haven't taken a 2003 exam yet. Still, never hurts to know how by hand.