Question

Construction of a building: Raman is a contractor; he is constructing a building of many floors. The building has interesting design on each floor it has open space thus number of rooms decreases as we go up. If number of bricks for construction of a room is 1500. The number of bricks required for ground floor is 30,000 on 1st floor it is 27,000 on 2nd floor It is 24,000 …… and so on i) Find the number of rooms on 5th floor.

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Answer 1

Answer:

20, 24, 23, 25, 26 27 28 29

Answer 2

$Given \: number \:of \: bricks \: required \\to \: construction \: of \:a \:room = 1500 \: --(1)$

$The \: number \: bricks \: required \: for \\ground \: floor = 30000$

$The \: number \: bricks \: required \: for \\first\: floor = 27000$

$The \: number \: bricks \: required \: for \\Second\: floor = 24000$

$Here, 30000, 27000, 24000, \ldots \: is \: an \:A.P$

$First \:term (a = a_{1} ) = 30000$

$Common \: difference (d) \\= a_{2} - a_{1} \\= 27000 - 30000 \\=- 3000$

$Number \: bricks\: required \: for \\5^{th}\: floor (a_{6}) = a + 5d \\= 30000 + 5 \times (-3000) \\= 30000 - 15000 \\= 15000\: --(2)$

$\red{ \therefore Number \: of \: rooms \:on }\\\red{ 5^{th} \: floor } = \frac{ (2)}{(1)} \\= \frac{15000}{1500} \\\green { = 10 }$

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