 Hello and welcome to the session. Let us construct a right triangle whose base is 12 cm and some of its hypotenuse and other side is 18 cm. So first let us draw a rough figure of how we are going to construct the triangle. Suppose this is triangle ABC. Here we have given that the base is 12 cm and AC plus AB is equal to 18 cm. So to construct this right triangle we shall follow the construction 11.4 of your book which says to construct a triangle given its base a base angle and the sum of other two sides. So let us see how we are going to proceed on with the construction. First we shall draw a ray BX then we shall mark a point C on it such that BC is equal to 12 cm then we shall draw angle YBC is equal to 90 degrees then we shall mark a point D on it such that BD is equal to the sum of other two sides that is 18 cm then we shall draw DC. Now we shall find the perpendicular bisector of line DC such that it intersects the line segment BD at a point A. So let this perpendicular bisector be PQ and in the last step we shall join A to C to get the required triangle. So this is the required triangle ABC such that AB plus AC is equal to 18 cm and the base is 12 cm. Now let us write the steps of construction and side by side construct the triangle. The first step is to draw a ray BX and mark a point BC is equal to 12 cm. The first we shall draw a ray BX C such that BC is equal to 12 cm since it is not possible to draw 18 cm and 12 cm on this board therefore you try it out yourself at proper measurements. Now our second step is to construct angle YBC is equal to 90 degrees with the help of a D or a protractor. So thus we have drawn angle YBC is equal to 90 degrees. Now we shall mark a point on the ray BY BD is equal to 18 cm. So let us take a point D on this line such that BD is equal to 18 cm. In the next step join DC we shall draw the perpendicular bisector let it be PQ of line segment DC such that it intersects the ray PQ of line segment DC for the point of intersection we call it as A and lastly we shall join A to C to get the required triangle. So in the last step we shall join AC and hence triangle ABC is the required triangle. This completes the session. So hope you have understood the construction take proper measurements while doing this construction of triangles. Take care and enjoy yourselves.