Q4 of 19 Page 91

Solve the following riddle:

I am a number,


Tell my identity!


Take me seven times over


And add a fifty!


To reach a triple century


You still need forty!

Let us assume the number be x


So, according to the riddle given in the question:


(7x + 50) + 40 = 300


7x + 90 = 300


7x = 300 – 90


7x = 210


Now,


We have to divide both the sides by 7


=


7x = 210


x = 30


Hence,


The required number be 30


More from this chapter

All 19 →
4

Construct 3 equations starting with x = - 2.

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


(f) Notebooks he has from 50, he finds the result to be 8.


(g) Ibenhal thinks of a number. If she adds 19 to it and divides the sum by 5, she will get 8.


(h) Anwar thinks of a number. If he takes away 7 from of the number, the result is 23.

2

Solve the following :


(a) The teacher tells the class that the highest marks obtained by a student in her class is twice the lowest marks plus 7. The highest score is 87. What is the lowest score?


(b) In an isosceles triangle, the base angles are equal. The vertex angle is 40o. What are the base angles of the triangle? (Remember, the sum of three angles of a triangle is 180o).


(c) Sachin scored twice as many runs as Rahul. Together, their runs fell two short of a double century. How many runs did each one score?

3

Solve the following:

(i) Irfan says that he has 7 marbles more than five times the marbles Parmit has. Irfan has 37 marbles. How many marbles does permit have?


(ii) Laxmi’s father is 49 years old. He is 4 years older than three times Laxmi’s age. What is Laxmi’s age?


(iii) People of Sundargarm planted trees in the village garden. Some of the trees were fruit trees. The number of non-fruit trees were two more than three times the number of fruit trees. What was the number of fruit trees planted if the number of non fruit trees planted was 77?