Question

2. The perimeter of a triangle is 40 cm. Two of its sides measure 12.9 cm and 14.6 cm. Find
the length of its third side.​

Answer 1

Answer:

Measure of the 3rd side = 12.6 cm

Step-by-step explanation:

$\longrightarrow$Perimeter = Side + 2nd Side + Side

$\longrightarrow$40 = 12.9 + 14.6 + 3rd Side

$\longrightarrow$40 = 27.5 + 3rd Side

$\longrightarrow$3rd Side = 40 - 27.5

$\longrightarrow$3rd Side = 12.6cm

Answer 2

AnswEr-:

• $\underline {\dag{\pink{\mathrm { Side\:C\:Third\:Side\:of\:Triangle\:is\:= 12.5 \:cm }}}}$

Explanation-:

$\mathrm {\bf{ Given-:}}$

• Side A or First Side of a Triangle is 12.9 cm.

• Side B or Second Side of a Triangle is 14.6 cm

• Perimeter of Triangle is 40 cm .

$\mathrm {\bf{ To\:Find -:}}$

• Side C or Third Side of Triangle.

$\sf{\bf{\dag{ Solution \:of\:Question \:-: }}}$

$\underbrace {\mathrm {\bf{ Understanding \:The\:Concept \:-:}}}$

• We have to find Third Side of Triangle when First Side and Second Side of Triangle is Given .

• For This Put the known Values in the Formula for Perimeter of Triangle.

• By this we can get the Third Side of Triangle.

________________________________________

$\underline {\sf{\bf{\dag{ Finding \:Third \:Side \:of\:Triangle \:-:}}}}$

As , We know that ,

• $\underline{\boxed{\star{\sf{\blue{ Perimeter _{( Triangle)} = Side \: A + Side \:B + Side \:C }}}}}$

$\mathrm {\bf{ Here-:}}$

• Side A or First Side of a Triangle is 12.9 cm.

• Side B or Second Side of a Triangle is 14.6 cm

• Perimeter of Triangle is 40 cm .

• Side C or Third Side of Triangle is ??

Now by putting known Values in Formula for Perimeter of Triangle-:

• $\qquad \quad \qquad \quad \longmapsto {\mathrm { 40\:cm \:= \: 12.9+ 14.6 + Side \: C }}$

• $\qquad \quad \qquad \quad \longmapsto {\mathrm { 40\:cm \:= \: 27.5 + Side \: C }}$

• $\qquad \quad \qquad \quad \longmapsto {\mathrm { 40\:-27.5 \:= \: Side \: C }}$

• $\qquad \quad \qquad \quad \underline {\boxed{\pink{\mathrm { Side\:C = 12.5 \:cm }}}}$

Hence,

• $\underline {\dag{\pink{\mathrm { Side\:C\:Third\:Side\:of\:Triangle\:is\:= 12.5 \:cm }}}}$

_________________________________________

$\Large {\mathrm {Verification \:\red{♡}-:}}$

As , We know that ,

• $\underline{\boxed{\star{\sf{\blue{ Perimeter _{( Triangle)} = Side \: A + Side \:B + Side \:C }}}}}$

$\mathrm {\bf{ Here-:}}$

• Side A or First Side of a Triangle is 12.9 cm.

• Side B or Second Side of a Triangle is 14.6 cm

• Perimeter of Triangle is 40 cm .

• Side C or Third Side of Triangle is 12.5 cm

Now by Putting known Values in Formula for Perimeter of Triangle-:

• $\qquad \quad \qquad \quad \longmapsto {\mathrm { 40\:cm \:= \: 12.9+ 14.6 + 12.5 }}$

• $\qquad \quad \qquad \quad \longmapsto {\mathrm { 40\:cm \:= \: 12.9+ 27.1 }}$

• $\qquad \quad \qquad \quad \underline {\boxed{\pink{\mathrm { 40cm = 40 \:cm }}}}$

Therefore,

• $\qquad \quad \qquad \quad:\implies {\mathrm { L.H.S = R.H.S }}$

• $\qquad \quad \qquad \quad:\implies {\mathrm { Hence \:, Verified \:! }}$

____________________________________________________

$\large { \boxed {\cal |\:\:{\underline {More \:To\:Know\:-:}}\:\:|}}$

• Area of Rectangle = Length × Breadth sq.units

• Area of Square = Side × Side sq.units

• Area of Triangle = ½ × Base × Height sq.units

• Area of Trapezium = ½ × Height × ( a +b ) or Sum of Parallel sides sq.units

______________________________________________________