the ratio between the present ages of a and b is 7: 3 respectively. the ratio between a ' s age 4 years ago and b ' s age 4 years hence is 1: 1. what is the ratio between a ' s age 4 years hence and b ' s age 4 years ago?	Choose one:
A) 3 : 4	B) 3 : 0	C) 9 : 1	D) 9 : 2	E) 3 : 9
<gadget id="calculator">7 + 7</gadget>
<output>14</output>

<gadget id="calculator">7 - 3</gadget>
<output>4</output>

<gadget id="calculator">14 / 4</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">7 * (7/2)</gadget>
<output>49/2 = around 24.5</output>

<gadget id="calculator">(49/2) + 7</gadget>
<output>63/2 = around 31.5</output>

<gadget id="calculator">3 * (7/2)</gadget>
<output>21/2 = around 10.5</output>

<gadget id="calculator">(21/2) - 7</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">(63/2) / (7/2)</gadget>
<output>9</output>

<result>C</result>
the ratio between the present ages of a and b is 7: 3 respectively. the ratio between a ' s age 4 years ago and b ' s age 4 years hence is 1: 1. what is the ratio between a ' s age 4 years hence and b ' s age 4 years ago?
divide(add(multiply(7, divide(add(7, 7), subtract(7, 3))), 7), subtract(multiply(3, divide(add(7, 7), subtract(7, 3))), 7))
"let the present ages of a and b be 7 x and 3 x years respectively . then , ( 7 x - 4 ) / ( 3 x + 4 ) = 1 / 1 4 x = 8 = > x = 2 required ratio = ( 5 x + 4 ) : ( 3 x - 4 ) = 18 : 2 = 9 : 1 . answer : c"