1.   Set up equations and solve them to find the unknown numbers in the following cases:
(a) Add 4 to eight times a number; you get 60.
(b) One-fifth of a number minus 4 gives 3.
(c) If I take three-fourths of a number and add 3 to it, I get 21.
(d) When I subtracted 11 from twice a number, the result was 15.
(e) Munna subtracts thrice the number of notebooks he has from 50, he finds the result to be 8.
(f) Ibenhal thinks of a number. If she adds 19 to it and divides the sum by 5, she will get 8.
(g) Anwar thinks of a number. If he takes away 7 from 5/2  of the number, the result is 23.

Answers (1)

Let the number in each case be n.

(a)  According to question:           8n\ +\ 4\ =\ 60

or                                                             8n\ =\ 60\ -\ 4\ =\ 56

or                                                               n\ =\ 7

 

(b) We have :          

                                          \frac{n}{5}\ -\ 4\ =\ 3

or                                       \frac{n}{5}\ =\ 7

or                                       n\ =\ 35

 

(c)  The equation is :

                                        \frac{3n}{4}\ +\ 3\ =\ 21

or                                    \frac{3n}{4}\ =\ 18

or                                      n\ =\ 24

 

(d)  We have :  

                         2n\ -\ 11\ =\ 15

or                                    2n\ =\ 26

or                                      n\ =\ 13

 

(e)  The equation is :

                           50\ -\ 3n\ =\ 8

or                                       3n\ =\ 42

or                                         n\ =\ 14

 

(f)  We have : 

                            \frac{n+19}{5}\ =\ 8

or                           n\ +\ 19\ =\ 40

or                                   n\ =\ 21

 

(g) We have :

                          \frac{5n}{2}\ -\ 7\ =\ 23

or                                    \frac{5n}{2}\ =\ 30

or                                      n\ =\ 12            

 

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