How to subtract LCD - 13/20 - 2/5

13/20 - 2/5 = 1/4 ( Using LCD)

Step-by-step explanation:

Given: 13/20 - 2/5 = ? Use LCD

1) First we need find the least common multiple of the denominator (20 and 5) which is 20.

2) Since we know the least common multiple we know need to switch the two fractions up but since one of the denominator is already 20 ( 13/20) we now need to fix the other fraction (2/5).

3) We need to make it the same for both fractions so we want the same denominator as the first fraction (20) so we multiply 5 by 4 since 5 x 4 = 20 and we get 20, while also doing the same thing with the numerator. So we times 2 by 4 and we get 8.

4) Now our two fractions are now 13/20 and 8/20.

5) Our next step is to subtract the numerator, so its 13-8 which we get 5.

6) So now we have 5/20 and we want to simply to the smallest fraction so we find a number that is divisible and can make the smallest fraction which is 5.  

5/5 and 20/5 and we get 1/4.

step-by-step explanation: so we look at the formula un = a + (n-1)d

un is the amount of seats

n is the nth term aka row number

a is the original sequence/row number

d is the difference between each term

so in this a=22 d=6 and n can remain as n because we are simply formjng a rule

lets put these in the equation

un=22+(n-1)(6)

this is your answer to part a

however

lets double check that this is correct, we'll try putting it into the second term

un=a+(n-1)d

u2=22+(2-1)(6)

u2=22+6

u2=28

as the question said the second row has 28 seats so now we know the formula we made is correct.

as for part b

un=a+(n-1)

its asking us to find a row with 100 seats.

remember un was the amount of seata so all we do is substitute this in.

un=100 a=22 d=6

un=a+(n-1)d

100=22+(n-1)(6)

so now we simplify to find n which is the row number.

100-22=22+(n-1)(6)-22

78=(n-1)(6)

78/6=(n-1)(6)/6

13=n-1

13+1=n-1+1

14=n

so now we know that in the 14th row there is 100 seats.

hope this and that you understood! its my first time using the app or anyone out on here : p its also me to revise so a bunch! ask more questions if you dont understand ☺

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step-by-step explanation: