Father = 4 &times; Harry. The model shows Harry as 1 unit and Father as 4 units.<br><br>&bull; Harry = 9 years (1 unit)<br>&bull; Father = 4 &times; 9 = 36 years<br>&bull; Total = 9 + 36 = 45 years<br><br>Their total age is 45 years.<br>Check: 36 &divide; 9 = 4. &#10003;