S.chand publication New Learning Composite mathematics solution of class 7 Chapter 15 Data Handling Exercise 15A

 Exercise 15A

Question 1

Her mean score

= (80+85+90+71+60+100)/6

= 81

Question 2

His mean score =

(138+144+155+142+167+172)/6

= 153

Question 3

(a)

 1^st 5 natural no – 1, 2, 3, 4, 5

Mean = (1+2+3+4+5)/5

= 15/5

=3

(b) 

1^st 7 whole no – 0, 1, 2, 3, 4, 5, 6

Mean = (0+1+2+3+4+5+6)/7

= 21/7

= 3

(c)

First 4 prime numbers are 2,3,5,7

Mean of 1st 4 prime numbers $=\frac{2+3+5+7}{4}$

=4.25

(d)

Mean$=\frac{7+19+31+43+70}{5}$

=34

Question 4

Mean number of hours$=\dfrac{2\frac{1}{2}+3\frac{1}{4}+2\frac{3}{4}}{3}$

$=\dfrac{\frac{5}{2}+\frac{13}{4}+\frac{11}{4}}{3}$

$=\dfrac{\frac{10+13+11}{4}}{3}$

$=\dfrac{\frac{34}{4}}{3}$

$=\frac{34}{12}=\frac{17}{6}$

$=2\frac{5}{6}$

Ans : Mean number of hour she worked on these three days is $2\frac{5}{6}$ hour

Question 5

Shika's mean score$=\frac{68+75+70+45+57+77}{6}$

=65.33

Bharti's mean score$=\frac{522+87+64+53+74+81+86}{7}$

=71

Ans : Bharti has higher mean score

Question 6

1st ten odd natural numbers =1,3,5,7,9,11,13,15,17,19

Mean of them$=\frac{1+3+5+7+9+11+13+15+17+19}{10}$

$=\frac{100}{10}$=10

Question 7

According to question

$=\frac{16+14+x+23+20}{5}=18$

16+14+x+23+20=18×5

73+x=90

x=90-73

∴x=17

Question 8

ATQ,

$\frac{x+(x+2)+(x+4)+(x+6)+(x+8)}{5}=24$

$\frac{x+x+2+x+4+x+6+x+8}{5}=24$

5x+20=24×5

5x+20=120

5x=120-20

$x=\frac{100}{5}=20$

Question 9

Let , her next test number be x

According to statements, $=\frac{73+86+78+75+x}{5}=80$

312+x=80×5

312+x= 400

x= 400–312

x= 88

Ans: – She should secure 88 marks in her next test.

Question 10

The mean of 6 number=24

∴The sum of 6 number=24×6=144

If one number is excluded, the mean of remaining number =22

∴The sum of remaining five number=22×5=110

∴The excluded number=144-110=34

Question 11

Mean weight of 20 students=48 kg

Sum of total weight 20 students=(48×20)=960 kg

Two more students join the class

∴Sum of weight of 22 students=(960+60+58)=1078 kg

∴The mean weight of the class$=\frac{1078}{22}$ kg

=49 kg

Question 12

(a)

$=\frac{(30 \times 8)+(31 \times 10)+(32 \times 15)+(33 \times 8)+(34 \times 9)}{8+10+15+8+9}$

$=\frac{240+310+480+264+306}{50}$

$=\frac{1600}{60}$

=32

(b)

$=\dfrac{(2\times 2)+(5\times 4)+(7\times 6)+(8\times 3)}{2+4+6+3}$

$=\frac{4+20+42+24}{15}=\frac{90}{15}$

=6

(c)

$=\dfrac{(13\times 8)+(15\times 2)+(17\times 3)+(9 \times 4)+(21 \times 5)+(23 \times 6)}{8+2+3+4+5+6}$

$=\frac{104+30+51+76+105+138}{28}=\frac{504}{28}$

=18

(d)

Mean marks$=\frac{(16 \times 1)+(17\times 1)+(18\times 3)+(19\times 1)+(20\times 5)+(22\times 3)+(23\times 5)+(24\times 4)+(25\times 2)}{1+1+3+1+5+3+5+4+2}$

$=\frac{16+17+54+19+100+66+115+96+50}{25}=\frac{533}{25}$

=21.32