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NCERT Solutions Class 9 Mathematics Solutions for Heron’s Formula - Exercise 12.2 in Chapter 12 - Heron’s Formula
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A floral design on a floor is made up of 16 tiles which are triangular, the sides of the
the triangle is 9 cm, 28 cm, and 35 cm (see Fig. 12.18). Find the cost of polishing the tiles at the
rate of 50p per \mathrm{cm}^{2}
Answer:
The semi perimeter of the each triangular shape = (28 + 9 + 35)/2 cm = 36 cm
By using Heron's formula,
The area of each triangular shape will be
Video transcript
"hello students welcome to leader q a
video session
i am seth your math tutor and question
for today is
a floral design on a floor is made up of
16 tiles
which are triangular the sides of the
triangle is 9 centimeter 28 centimeter
and 35 centimeter
you can see the figure 12.18 find the
cost of polishing the tiles
at the rate of rupees 50 at the rate of
50 passes per
centimeter square so here first of all
we need to find semi perimeter
and then we will try to find area for
whole
figure so here semi perimeter will be
equal to
that is 28 plus 9 plus 35
remember this is the semi perimeter of
each triangular shape
that is 28 plus 9 plus 35
side there three sides are these
addition of three sides
so divided by two and that is semi
parameter s
and that is 36 centimeter
so s is 36 centimeter by using harold's
formula
the area of each triangle shape will be
root off
as s
minus a s minus
b as minus c
that is root of
s is 36 36 minus 35
and you have 36 minus 28
and then you have 36 minus 9
so it is root of 36
into 1 into 8 into 27
centimeters square this is our
area of each triangle shape
so in the next step i'll write down here
our answer for this is 36 root 6
centimeter square that will be 88.2
centimeter
square
now this is area of each triangle shape
now the total area
of 16 tiles will be equal to 16 into
area of one type
that is area of each shape let us
continue over here
16 into 88.2
that is 1411.2
centimeter square that is the area of 16
times
now the cost of per tile polishing is
given that is 50
per centimeter square
so simply what is the cost of polishing
16
times
for that we need to multiply that area
of 16 tiles
into cost per centimeter square it is
1411.2
into 50
or this 50 is per se so you can write
here in rupees as 0.5 rupees
and the answer will be coming in rupees
now
so 1411.2
into 0.5 will be equal to
705.6 rupees
hence cost of polishing
16 tiles
is equal to 705.6
rupees that is our final answer if you
have any query you can post it in our
comment section
and subscribe to lido for more such q a
thank you for watching
"
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