Question

If $a=1\frac{5}{7},b=\frac{1}{4},c=\frac{1}{9}andd=(-1\frac{1}{4})$, then $a(b-c)÷d$= ___.

• A. $-\frac{4}{21}$
  
  
• B. $-\frac{6}{23}$
• C. $-\frac{5}{27}$
• D. $\frac{5}{21}$

Answer 1

The correct option is A $-\frac{4}{21}$



Given that$a=1\frac{5}{7},b=\frac{1}{4},c=\frac{1}{9}andd=(-1\frac{1}{4}).$
i.e., $a=\frac{12}{7},b=\frac{1}{4},c=\frac{1}{9},d=-\frac{5}{4}$

$a(b-c)÷d=\frac{12}{7}(\frac{1}{4}-\frac{1}{9})÷-\frac{5}{4}$
$=\frac{12}{7}\left(\frac{9-4}{36}\right)\times -\frac{4}{5}$
$=\frac{12}{7}\left(\frac{5}{36}\right)\times -\frac{4}{5}$
$=\frac{5}{21}\times -\frac{4}{5}$
$=-\frac{4}{21}$