Question 1208933
.


        Use the watch dial.


<pre>
1/3 of an hour is 20 minutes.


1/4 of an hour is 15 minutes.


The sum  1/3 + 1/4  is  20 minutes + 15 minutes = 35 minutes,  or 7/12 of an hour.


In fractions, it corresponds to  fraction addition 

    {{{1/3}}} + {{{1/4}}} = work with the common denominator = {{{4/12 + 3/12}}} = {{{7/12}}},


giving you the same value as the watch dial gives visually.
</pre>


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Then you can continue your explanations this way.


<pre>
Draw first  vertical rectangle with the horizontal base of 1 cm and vertical height of 4 cm.

Draw second vertical rectangle with the horizontal base of 1 cm and vertical height of 3 cm.

Draw third  vertical rectangle with the horizontal base of 1 cm and vertical height of 12 cm.


First  rectangle represents 1/3 of the third rectangle.

Second rectangle represents 1/4 of the third rectangle.


    +------------------------------------------------------------+
    |     So, first rectangle and second rectangle represent     |
    |        fractions 1/3 and 1/4, which you want to add.       |
    +------------------------------------------------------------+


Divide/separate each of the three rectangle by horizontal segments 1 cm of height each.
These small rectangles all have the same measure: this common measure is 1/12 
of the measure of the great rectangle.


Then you see that first rectangle is 4 times the common measure,
while the second rectangle is 3 times the common measure.

The sum of the first and the second rectangles is 4+3 = 7 times the common measure.

This corresponds to fraction addition

    {{{1/3}}} + {{{1/4}}} = work with the common denominator = {{{4/12 + 3/12}}} = {{{7/12}}},

giving the same value as you got using the diagram.
</pre>

---------------------


Solved, answered and explained.


These two explanations are just enough.


It is the way on how my grandmothers and grandfathers were taught more than 100 years ago.