10 2/5 times 15 5/7 is 5,720/35 which is 163 15/32 in mixed number
Steps
find the Least Common Multiple of the denominators (which is called the Least Common Denominator).
Change each fraction (using equivalent fractions) to make their denominators the same as the least common denominator.
Then add (or subtract) the fractions, as we wish!
your denominators stay the same so its 20
It depends on what you are trying to calculate but the most common way I go to find percentage is to multiply by the number in decimal for ie. 50% = .5.
If you are looking for a way to do it quickly in your head I always take find out what 10% is like in the case of 100 it would be 10 so if I want to find 15% I know I can find 10% and if I cut what 10% is in half I will find 5% so likewise if I add what 10%+5% I will end up with 15%. For example, 10% of 100 is 10 half of 10 is 5 and 10+5 equals 15. If you need to find something like 20% or 30% I know that I can find 10% and instead of dividing(cutting it in half) I can multiply by 2 or 3. 10% + 10% =20%
I hope it helps, if you have more questions let me know!
Data:
Formula: diameter = 2*radius
Formula: (<span>Circle length)
</span>

<span>
Solving: </span><span>Using the data
</span>diameter = 2*radius
20 = 2*r
2r = 20


<span>Now, replace in the circumference length formula
</span>



Answer:
<span>
The exact circumference of the circle is </span>