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Question 1022846: My sister is 9 1/2 years old. My brother is 4 3/4 years younger than my sister how old is my brother show me the answer and how to get it
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! sister is 9 and 1/2 years old.
brother is 4 and 3/4 years younger than sister.
you need to subtract 4 and 3/4 from 9 and 1/2 to get the brother's age.
you can convert them both to improper fractions first of all.
9 and 1/2 is equal to (2 * 9 + 1) / 2 = 19/2.
4 and 3/4 is equal to (4 * 4 + 3) / 4 = 19/4.
now you want to convert them both to fractions with the same denominator.
19/2 * 2/2 = 38/4.
you now have 38/4 is the age of the sister, and 19/4 is how much younger the brother is.
now subtract the number of years that the brother is younger to get:
38/4 - 19/4 = 19/4.
the brother is 19/4 years old.
convert that to a mixed fraction and you get:
the brother is 4 and 3/4 years old.
it looks like the brother is just half the age of the sister.
you can always confirm using your calculator.
the sister is 9 and 1/2 years old.
convert that to a decimal and you get 9 and 1/2 = 19/2 = 9.5 years old.
4 and 3/4 years is equal to 19/4 = 4.75 years.
9.5 years minus 4.75 years is equal to 4.75 years.
the brother is 4.75 years old.
this is exactly half of 9.5 because 4.75 / 9.5 = 1/2.
the calculator confirms the manual solution is correct.
presumably this was a lesson in subtracting mixed fractions.
there are other ways of doing mixed fractions.
here's another.
you want to subtract 4 and 3/4 from 9 and 1/2.
comvert the fractions to the same common denominator.
you want to subtract 4 and 3/4 from 9 and 2/4.
since you want to subtract 3/4 from 2/4, you need to borrow a whole number so that the fractional part of the number you want to subtract from is bigger than the fractional part of the number you want to subtract.
from 9 and 2/4, borrow 1 and convert it to 4/4 and add it to 2/4.
the result sill be 8 and 6/4.
you subtracted 1 from the whole part of the number and you added the equivalent value of 4/4 to the fractional part of the number.
now you want to subtract 4 and 3/4 from 8 and 6/4.
subtract the whole parts and subtract the fractional parts and then combine them into your answer.
8 minus 4 = 4.
6/4 - 3/4 = 3/4.
your answer is 4 and 3/4.
i personally prefer to make them improper fractions and then give them the same common denominator and then do the subtraction.
this other method also works.
it's according to your preference.
the logic of the problem says that if i'm a certain age, and you're a certain number of years younger than me, then you age has to be my age minus the difference in the number of years.
example:
i'm 18 and you're 6 years younger.
your age is 18 - 6 = 12.
i'm 18 and you're 12.
you have to be 18 - 12 = 6 years younger.
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