evaluate (-2 3/4) x 4/5

Question

my daughter started 7th grade today and we are perplexed by this question. she is unsure of what to do as am I

Answer 1

(-2 3/4)*(4/5)

change the mixed number into an improper fraction

2 3/4=(2*4+3)/4

2 3/4=11/4

-2 3/4=-11/4

now you have two fractions to multiply together

the answer will be negative because a negative times a positive is negative

(11/4)*(4/5)=(11*4)/(4*5)=44/20=2 4/20=2 1/5

the answer is -2 1/5

you can and should simplify before you multiply

you have a 4 in the denominator of the first fraction and a 4 in the numerator of the second fraction

these can be cancelled out leaving (11/1)(1/5)=(11*1)/(1*5)=11/5=2 1/5 and again the answer is negative, -2 1/5

when you simplify before multiplying make sure one common factor is in a numerator and the other common factor is in the denominator

Answer 2

to evaluate this you are first going to want to put the -2 3/4 into a fraction

it will be an improper fraction but we will take take of that later

 

each whole is four quarters so 1 = 4/4, 2 = 8/4, 2 3/4 = 11/4

 (I will show you another way to get that at the end)

 

Now you have 11/4 times 4/5

- 11 x  4  =

   4      5

 

now multiply both the tops (numerators) and bottoms (denominators)

 

-11 x 4 =  44

 4  5     20

 

Now reduce the improper fraction 44/20

 by dividing 20 into 44 -or- dividing 44 by 20 [what ever way you think of it]

 

-44/20 = -2 4/20 = 2 1/5

 

Now back to that beginning step.

The mathematical ay to do it will get answers when something is

not as easy as knowing 1 = 4/4 and 2 = 8/4

 

Take the 2 3/4 and make it an addition

2 + 3   see the bottom (denominator) of the right (4)?

      4   multiply the left 2 by 4/4 you can do that because 4/4 is = 1

 

4*2 + 3 = 8 + 3 = 11   then use 2 3/4 = 11/4 like before

4      4     4    4      4