1.

28) Find the value of(a) 1 + (-2) + (-3) + (-4)(b) (-50) - (-60) + 50(c) (-30) - 45 -- 2529) The number of boys and girls in a school are 390 and 520 respectively. Findthe ratio of(a) Number of girls to the number of boys.(b) Number of boys to total number of students.(c) Total number of students to the number of girls.30) A rectangular hall is 80 m long and 35 m wide. Find its area and also findthe cost of tiling the hall at 24 per square metre.ORFind the peririeter of the following shapes.(a) A triangle of sides 4 cm, 6 cm, 7 cm(b) An equilateral triangle of side 9 cm.(c) A regular pentagon with each side 8 m​

Answer»

\underline\bold\red{Answer:}

28)

(a) -8

(B) 50

(c) -100

29)

(a) \frac{3}{4}

(b) \frac{3}{7}

(c) \frac{7}{4}

30) 2800 m², ₹67,200

OR

(a) 17 cm

(b) 18 cm

(c) 40 cm

\underline\bold\red{Step-by-step\: explanation:}

28)

(a) 1 + (-2) + (-3) + (-4) = 1 - 2 - 3 - 4

= 1 - 9

= -8

(b) (-50) - (-60) + 50 = -50 + 60 + 50

= 50 (minus and plus getting CANCELLED)

(c) (-30) - 45 - 25 = -30 - 70 = -100

29)

(a)

Ratio \: of \: no. \: of \: girs \: to \: the \:number \: of \: boys = \frac{390}{520} = \frac{3}{4}

(b)Ratio \: of \: number \: of \: boys \: to \: total \: number \: of \: students = \frac{390 }{910} = \frac{3}{7}

(c)

Ratio \: of \: total \: number \: of \: students \: to \: the \: number \: of \: girls = \frac{910}{520} = \frac{7}{4}

30)

Area of rectangle = l x b

= 80 x 35 = 2800 m²

Cost of tiling the hall per square metre = ₹24

Cost of tiling the hall 2800 square metre = 24 x 2800

= ₹67,200

OR

(a) Perimeter of scalene triangle

= a + b + c

= 4 + 6 + 7

= 17 cm

(b) Perimeter of equilateral triangle

= 3 a

= 3 x 9

= 18 cm

(c) Perimeter of regular Pentagon

= 5 a

= 5 x 8 = 40 cm


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