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a. Okay. So we have to make a table for the amount of butterflies to total insects. Let's simplify the ratio. 36:100 simplifies to 9:25. We can use that ratio to make this table. Just multiply 25 by the amount it takes to get to 50 or 100, and multiply by the same amount at the top to find the amount of butterflies. If you do it correctly, your table should be as shown below in the image.
b. On that note, let's solve for the amount of butterflies in the conservatory. There are 450 total of them. Let's divide 450 by 100 to find the amount we will multiply by. 450/100 is 4.5. We will mutliply 36 by that amount to find the total amount of butterflies. 36 * 4.5 is 162. That's it. There are 162 butterflies in the conservatory.
To calculate this probability is often easier to calculate the complement
the prob that we are looking for is 1-P(No salt packed in dinner)
Note: No salt packed with dinner is the complement event of having salt packed within
so let's find this probability
He is what we know
if John packs 4/45 chance no salt included
if Sue packs 3/70 chance no salt
if Marry packs 2/25 No salt
We are looking into probability is the sum (note these events are disjoint)
final result should be 1- that sum
Multiplication is a simple way of adding
For example 6x8 is the same as 8+8+8+8+8+8
Any number multiplied by 1 is itself E.g 4x1 = 4
Multiplying by 2 is just doubling
Multiplying by 10 is adding a 0 to the original number
If it is a big number that you do not know how to multiply mentally split it up
E.g 17x13
Split 13 into 10 and 3
17x10= 170
17x3= 51
Then add these numbers
221
If you ever get stuck, use the long method, add them instead, you will get to the right answer but it will take longer
Dividing is not as simple
Like multiplication dividing by one will leave you with the same answer
Dividing by two means you half the number, which may give you a decimal
Bigger numbers are trickier, and you may be allowed to use a calculator for numbers
Below are a number of links, these websites will teach you how to improve your multiplication and division skills:
http://www.bbc.co.uk/schools/gcsebitesize/maths/number/decimalsrev3.shtml
https://m.youtube.com/watch?v=XiXeu9FxAcQ
https://www.tutorialspoint.com/multiply_and_divide_whole_numbers/multiplication_as_repeated_addition.htm