# Thread: help on some math questions???anyone?

1. ## help on some math questions???anyone?

I have some math questions:
Reform the indicated operation. write in lowest terms.
#8. 2 2/5 times 1 6/7?
#10. 2 2/5 divide 6?
#12. 1 1/6+4 3/5?
#14. 50 1/4-32 2/3?
#20. what is the least common denominator for 3/4 and 2/7?
Does any one know these? it would be greatly appreciated. thank you.

2. I don't KNOW any of those. They require a bit of calculation.

Multiply mixed fractions by makign them improper fractions. Then multiply numerators and denominators. There may be reductions and simplifications along the way.

#8. 2 2/5 times 1 6/7?

2 2/5 = 12/5

1 6/7 = 13/7

(12/5)*(13/7) = 156/35

Done. (Unless someone has a particular hatred for improper fractions)

3. Originally Posted by abb1327
I have some math questions:
Reform the indicated operation. write in lowest terms.
#8. 2 2/5 times 1 6/7?
#10. 2 2/5 divide 6?
#12. 1 1/6+4 3/5?
#14. 50 1/4-32 2/3?
#20. what is the least common denominator for 3/4 and 2/7?
Does any one know these? it would be greatly appreciated. thank you.
#8 $2\frac{2}{5} \cdot 1\frac{6}{7}$

Okay, let's get this straight: $2\frac{2}{5}$ is actually $2 + \frac{2}{5}$. How can you combine fractions, do you know? Let me remind you that in order to add fraction, both fractions must have the same denominator ( $\frac{Numerator}{Denominator}$).
$\frac{2}{1} + \frac{2}{5} = \frac{2 \cdot 5}{1 \cdot 5} + \frac{2}{5} = \frac{10}{5} + \frac{2}{5} = \frac{12}{5}
$

Can you continue?

#10
One hint: to divide by a number is the same as multiply by the reciprocal of a number. For instance:

12 ÷ 6 = 2

What is reciprocal of 6? $\frac{1}{6}$. What is reciprocal of 5 for instance? $\frac{1}{5}$.

Let's check:

$12 \cdot \frac{1}{6}. = \frac{12}{6} = 2$

20. Use prime factorization

I'm sure you can do them on your own now.

4. Hello, abb1327!

Preform the indicated operation. write in lowest terms.

$8.\;\;2\frac{2}{5} \times 1\frac{6}{7}$

With multiplication and division, we must convert to improper fractions.

We have: . $\begin{array}{ccc}2\frac{2}{5} &=& \frac{12}{5} \\ \\[-4mm]1\frac{6}{7} &=& \frac{13}{6} \end{array}$

Hence: . $2\frac{2}{5} \times 1\frac{6}{7} \:=\:\frac{12}{5}\cdot\frac{13}{6} \:=\:\frac{26}{5} \:=\:\boxed{5\frac{1}{5}}$

$10.\;\;2\frac{2}{5} \div 6$

We have: . $\begin{array}{ccc}2\frac{2}{5} &=&\frac{12}{5} \\ \\[-4mm] 6 &=& \frac{6}{1} \end{array}$

Hence: . $2\frac{2}{5} \div 6 \:=\:\frac{12}{5} \div \frac{6}{1} \:=\:\frac{12}{5} \times\frac{1}{6} \:=\:\boxed{\frac{2}{5}}$

$12.\;\;1\frac{1}{6} + 4\frac{3}{5}$

With addition and subtraction, we can try to work with the whole numbers
. . and the fractions separately.

. . $\begin{array}{ccc}& 1 & \frac{1}{6} \\ \\[-4mm]
+ & 4 & \frac{3}{5} \\ \\[-4mm]\hline \\[-4mm]& 5 & {\color{red}?} \end{array}$

We added the whole number: . $1 + 4 \:=\:5$

Now add the fractions: . $\frac{1}{6} + \frac{3}{5} \:=\:\frac{18}{30} + \frac{5}{30} \:=\:\frac{23}{30}$

Answer: . $\boxed{5\frac{23}{30}}$

$14.\;\;50\frac{1}{4} - 32\frac{2}{3}$

. . $\begin{array}{ccc} & 50 & \frac{1}{4} \\ \\[-4mm] - &32 & \frac{2}{3} \\ \\[-4mm] \hline \\[-4mm] & 18 & {\color{red}?}
\end{array}$

But we find that: . $\frac{1}{4} - \frac{2}{3}$ is negative . . . but this is not a problem!

Subtract: . $\frac{1}{4} - \frac{2}{3} \:=\:\frac{3}{12} - \frac{8}{12} \:=\:-\frac{5}{12}$

Hence, we have: . $18 - \frac{5}{12} \:=\:17 + 1 -\frac{5}{12} \;=\;17 + \frac{7}{12}$

Answer: . $\boxed{17\frac{7}{12}}$

20. What is the least common denominator for $\frac{3}{4}$ and $\frac{2}{7}$ ?
The denominators are 4 and 7.

The LCD is: . $4\!\cdot\!7\:=\:\boxed{28}$

This is a rather silly problem, isn't it?
We have supposedly completed nineteen problems already, with
. . multiplication, division, addition and subtraction of fractions.

And then they ask if we know to find a common denominator ??
. . Well, duh!

5. Soroban, $6 \neq 7$. Please review the first problem.

6. ## what happened?

wait what do you mean that 6 is not = to 7 where do u see that at?

7. Originally Posted by abb1327
wait what do you mean that 6 is not = to 7 where do u see that at?
$1\frac67 = \frac{13}7,$ not $\frac{13}6.$