Hey guys
.
.
.
plz solve this problems
plz... It's urgent...
Answers
Step-by-step explanation:
28.
radius of graphite , r = 0.5 mm = 0.05 cm.
radius of wooden part of pencil, R = 3.5 mm = 0.35 cm
length of pencil l = 10 cm
Volume of graphite = πr²l
= π(0.05)² * 10
= π × 25 * 10^-3 cm³
Weight of graphite = π * 25 * 10^-3 * 2.3
= 22/7 * 25 * 10^-3 * 2.3
= 165 × 10^-3
= 0.165
Volume of wooden part of pencil = π(R² - r²)l
= π(0.35² - 0.05²) * 10
= π(0.35 + 0.05)(0.35 - 0.05) * 10
= π * 0.4 * 0.30 * 10
= π * 1.2
weight of wooden part , w = π * 1.2 * 0.6
= 22/7 * 1.2 * 0.7
= 2.26
so, total weight of pencil = 2.26 + 0.165
= 2.4 g
29.
Circumference of inner circle = 88 cm
2πr = 88
2 * 22/7 * r = 88
r = 14 cm
Given,
Area between two concentric circles is 346.5 sq.cm.
π(R² - r²) = 346.5
=> 22/7(R² - r²) = 346.5
=> 22(R² - 14²) = 2425.5
=> R² - 196 = 110.25
=> R = 17.5 cm
Hope it helps!
Answer:
Step-by-step explanation:
Pencil Graphite
D = 7mm d = 1mm
R = 3.5 mm r = 0.5 mm
= 0.35cm = 0.05 cm
h = 10cm h = 10cm
volume of graphite = π r² h
= 22 /7 x 0.05 x0.05 x 10
= 0,079 cm³
volume of pencil = 22 /7 x 0.35 x0.35 x10
= 3.85 cm³
volume of wood = volume of pencil - volume of graphite
= 3.85 - 0,079
= 3.771 cm³
= 3.771 x 0.6
= 2.2626 g
volume of graphite = 0.079 x 2.3
= 0,1817 g
∴ weight of whole pencil = 2.2626 + 0.1817
= 2.4443 gm
29 ) inner circumference = 88
2π r = 88
2 x 22/7 x r = 88
r = ( 88 X7 ) / 2x22
= 14cm
area of concentric circle = 346.5 sq.cm
π (R² -r²) = 346.5
22/7 (R² - !4²) = 346.5
R² - 196 = 346.5 x 7/22
R² = 110.25 +196
= 306.25
R =√306.25
= 17.5 cm