Question

The length and breadth of a rectangle are 4.5 cm and 1.3 cm respectively. Find its area.​

Answer 1

Answer:

Step-by-step explanation:

Here, l=(5.7±0.1)cm,b=(3.4±0.2)cm

Area, A = l×b=5.7×3.4=19.38cm  

2

=19.0cm  

2

 (rounding off to two significant figures)

∴  

A

△A

​

=±(  

l

△l

​

+  

b

△b

​

)

= ±(  

5.7

0.1

​

+  

3.4

0.2

​

)=±(  

5.7×3.4

0.34+1.14

​

)=±  

19.38

1.48

​

 

⇒△A=±  

19.38

1.48

​

×A=±  

19.38

1.48

​

×19.38=±1.48

△A=±1.5 (rounding off to two significant figures);

Area = (19.0±1.5)cm  

Answer 2

Here, l=(5.7±0.1)cm,b=(3.4±0.2)cm

Area, A = l×b=5.7×3.4=19.38cm

2

=19.0cm

2

(rounding off to two significant figures)

∴

A

△A

=±(

l

△l

+

b

△b

)

= ±(

5.7

0.1

+

3.4

0.2

)=±(

5.7×3.4

0.34+1.14

)=±

19.38

1.48

⇒△A=±

19.38

1.48

×A=±

19.38

1.48

×19.38=±1.48

△A=±1.5 (rounding off to two significant figures);

Area = (19.0±1.5)cm

2

.