Question

A man was told to make a rectangular desk with top dimensions of 100cm to 80cm. The man actually made the desk 120cm by 70cm. Find the percentage error in the:
i). Length of the top of the desk.
ii). Breadth of the desk.
iii). Area of the desk.
iv). Perimeter of the desk.​

Answer 1

Answer:

Here, l=(5.7±0.1)cm,b=(3.4±0.2)cm

Area, A = l×b=5.7×3.4=19.38cm2=19.0cm2 (rounding off to two significant figures)

∴A△A=±(l△l+b△b)

= ±(5.70.1+3.40.2)=±(5.7×3.40.34+1.14)=±19.381.48

⇒△A=±19.381.48×A=±19.381.48×19.38=±1.48

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

Area = (19.0±1.5)cm2.

Answer 2

Answer:

Area = 100x80= 8000, Actual Area= 120x70= 8400

Perimeter= 2x(100+80)=360, Actual Perimeter= 2(120+70)=380

Step-by-step explanation:

i. (120-100)x100 ÷100= 20%

ii. (80-70)x100 ÷ 80 = 12.5%

iii. (8400-8000)x100÷8000= 5%

iv. (380-360)x100 ÷ 360= 5.55%