State Secondary Certificate – ( SSC BOARD )
Class – 8
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Recommended Question & Answers for Class 8
1. Factorize the following:
(ii) x3 + 2×2 + 5x + 10
(iii) m2 – mn + 4m – 4n
Answer:
i) 3ax – 6xy + 8by – 4ab
= (3ax – 6xy) – (4ab – 8by)
= (3 × a × x – 2 × 3 × x × y)
– (4 ×a × b – 4 × 2 × b × y)
= 3x(a – 2y) – 4b(a – 2y)
= (a – 2y)(3x – 4b)
ii) x3 + 2×2 + 5x + 10
= (x3 + 2×2) + (5x +10)
= (x2 × x + 2 × x2) + (5 × x + 5 × 2)
= x2(x + 2) + 5(x + 2)
= (x + 2) (x2 + 5)
iii) m2 – mn + 4m – 4n
= (m2 – mn) + (4m – 4n)
= (m × m – m × n) + (4 × m – 4 × n)
= m(m – n) + 4(m – n)
= (m – n) (m + 4)
2. Discuss the merits and demerits of using mirrors in building elevation ?
Merits:
1. The mirrors used in elevating building are tough, reinforced and laminated glasses so they provide safety to the building.
2. They make the building attractive.
3. They absorb heat energy, so they cool inside the building.
4. If we use plane mirrors in building elevation it is easy to wash with water and no need of regular painting.
Demerits:
1. Elevation of buildings with mirrors is not suggestible.
2. These mirrors reflect sun rays at day time and reflects lighting from near by electrical bulbs at night time, which causes confusion and disturbance for the vehicles and people who are running on the nearby roads lead to accidents.
3. Birds like sparrows, crows will get confusion while flying on roads.
4. They are also not safe enough to the buildings, which causes easy access to thieves.
5. This glass elevation is not environmental friendly, because natural air does not enter into the building.
6. They are easy to break and cause cuts and wounds.
3. Let us assume that you are on the moon. If you try to focus sunlight on a paper using magnifying glass, does the paper catch fire? or not? Why?
Answer:
No, moon reflect entire sunlight falls on the surface because it acts as perfect reflector. Whereas earth is also acts as reflector but green house gases present in atmosphere absorbing the sunlight and re-sending on earth. So paper can be burnt on earth by using magnifying glass but it is not possible on moon.