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Melody

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यूजर का नामMelody
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Melody  11 Feb 2022
 #1
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..fractions)::

.7813 into a proper fraction, like how can i get it to 25/32?



0.7813 has 4 digits after the decimal point so if you change it to a fraction it will be over 10,000 (4 zeros see)

= 7813 / 10,000 this cannot be simplified because no number goes into both 7813 and 10,000!
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Now. I think that 0.7813 has been rounded off to 4 decimal places. Originally I think it was 0.78125

0.78125 has 5 digits after the decimal point so when I change it to a fraction, it will be over 1 with 5 zeros. that is

78125 / 100,000

I can see straight away that 25 will go into both these numbers. That's because I know that if a number ends in 00 or 25 or 50 or 75 it will be divisable by 25.
so now I have to divide the top and the bottom by 25
78,125 divided by 25 is 3,125 and
100,000 divided by 25 is 4,000
so now I have

3,125 / 4000
I can see straight away that 25 will go into both these numbers. That's because I know that if a number ends in 00 or 25 or 50 or 75 it will be divisable by 25.
so now I have to divide the top and the bottom by 25
3125 divided by 25 is 125 and
4,000 divided by 25 is 160
so now we have

125 / 160
I can see straight away that 5 will go into both these numbers. That's because I know that if a number ends in 0 or 5 it will be divisable by 5.
so now I have to divide the top and the bottom by 5
125 divided by 5 is 25 and
160 divided by 5 is 32
so now we have

25 / 32

Each time you make the numbers in a fraction smaller like this you are CANCELLING it down.
26 Jan 2014
 #17
avatar+118691 
+15
Another day done,
some good answers were presented by I like Serena, kitty<3, Lucas, bechapm, DavidQD, and Anonymous4338.
Anonymous4338 pick up on it when I didn't interprete a question the way we both think it was meant. That was really great.
DavidQD gave a fantastic final answer to Walt's "My teacher wants to fail me" question. So now, Walt you should be able to 'knock your teacher's socks off'

Aadilk96 did the most recent number puzzle. That was really good to see.
I have posted two more puzzes on that same thread. They are similar but one is difficult and the other is much easier.
Take a look and answer, or ask for a hint, on the one that best suits your ability level. Playing with numbers really will help you to understand them better

'I like serena' answered the next bit on the 'what is a number divisable by post. He? was being a bit cheeky really, 'I like Serena' is a very good mathematician and I am hoping he/she will stay and answer lots of questions, especially the physics question. We would all really appreciate it if you stay and help us out. (Now I need a clapping emoticon, we don't have one, what a shame)

The last thing on my mind is that I would really like some people to think about what an appropriate title for their post might be.
It can make quite a big difference to how quickly your question is answered. It also makes a big difference to how easily it can be refound if it is not answered straight away.
There may have been an extreme case today. I like Serena was answering questions, with what appeared to be a preference for physics questions. Princess Sophie had posted a great physics question but the title was 'math'. I think 'i like serena' simply didn't see it and it is the only question that has not been answered today. If it had been called Physics or Forces, it probably would have been answered already.
That's it, for me it is Saturday evening, for most of you it is Friday night. So, have a great weekend.
25 Jan 2014
 #22
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0
I like Serena:

Hmm, if I have a big number like 3456, it can be written as 3x1000 + 456.
3x1000 and numbers with more zeroes are obviously divisible by 8.
In other words, if the last 3 digits are divisible by 8, the whole number is divisible by 8!
Yay!



Yes, very clever, I like Serena.
now lets see what we have.

Now for the divisability checks. What do we have so far?

1) We have Zamarronics's formula,

2) A number is exactly divisable by 10 if it has a zero at the end. (the last digit is zero)

3) A number is exactly divisable by 2 if it is even.

4) If a number is prime then it is only exactly divisable by 1 and itself

5) A number is exactly divisable by 5 if it ends in 0 or 5

6) A number is exactly divisable by 3 if the sum of its digits is exactly divisable by 3.

7) A number is exactly divisable by 9 if the sum of its digits is exactly divisable by 9

8) If the last 2 digits of a number are a multiple of 4, the whole number is exactly divisible by 4.

9) If the last 3 digits of a number are a multiple of 8, the whole number is exactly divisable by 8.
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Okay,
Here is a number 67,960,350
Without actually doing any (full) division, and without getting out a calculator, what are some of its factors.
That is, what numbers can it divided by without getting any remainders?
If you can't think of all of them maybe you can think of just a couple.
If you give reasons that would be good too.
25 Jan 2014