LINEAR EQUATIONS (LECTURE 7)

April 28, 2020

LINEAR EQUATIONS (LECTURE 7)

LINEAR EQUATIONS EX 2.4(II)

DEAR STUDENTS

WELCOME TO THE CLASS!!

Guidelines for the class:

1. Note down the work in your register on a regular basis.

2. Please feel free to ask, if you have any doubt by dropping a message in the comment box.

3. Make a column on the right hand side, if you need to do any rough work

4..Write today's date.

5.Write the chapter number and name.

6.Text in Blue has to be noted down.

Write down Today's Learning Outcomes

I will be able to:

. translate the word problems in the form of linear equations

.solve the linear equation to find the unknown.

TODAY WE WILL START WITH " 2 DIGIT NUMBER" PROBLEMS

YOU ALL KNOW WHAT ARE 2 DIGIT NUMBERS LIKE 34,67

LET'S UNDERSTAND ABOUT THEM THROUGH THIS LINK
so, you just saw a 2 digit no. can be written using its ones and tens place

LIKE 36 = 3X10+6

SO,any 2 digit number can be written as

xy = 10x+y .

note down and draw the table

IF X IS THE DIGIT AT ONES PLACE AND Y AT TENS PLACE

THEN NO. CAN BE WRITTEN AS 10X +Y

Remember digit means no.s FROM 0 to 9

if we reverse the digits , then units digit moves to tens place and tens digit to ones place

so no. becomes 10y+x

EG.The digits of a two-digit number differ by 3. If the digits are interchanged, and the resulting number is added to the original number, we get 143. What can be the original number?

let the digit at ones place be x

tens place be y

so, original 2 digit number is 10y+x

We are given,The digits of a two-digit number differ by 3.

so, if one digit is x then other is x +3

so number becomes 10(x +3) +x

simplifying. 10x + 30 + x= 11x +30

When we interchange digits, the no. becomes

now, we will do Q3 of EX 2.4

3. Sum of the digits of a two-digit number is 9. When we interchange the digits, it is found that the resulting new number is greater than the original number by 27. What is the two-digit number?

what are you looking for?

A 2 digit number.

So, let's take a 2 digit number be 10y +x where y is digit at tens place and x at ones place.

As, Sum of the digits of a two-digit number is 9

so, if one digit is x then other is 9 -x

Q6There is a narrow rectangular plot, reserved for a school, in Mahuli village. The length and breadth of the plot are in the ratio 11:4. At the rate `100 per metre it will cost the village panchayat ` 75000 to fence the plot. What are the dimensions of the plot

Let the length and breadth of the rectangular plot be and respectively.

Perimeter of the plot = = = 750 m

We know that Perimeter of rectangle = 2 (length + breadth)

Therefore, according to the question,

Hence, length of rectangular plot = = 275 m

And breadth of rectangular plot = = 100 m

7. Hasan buys two kinds of cloth materials for school uniforms, shirt material that costs him ` 50 per metre and trouser material that costs him ` 90 per metre.For every 3 meters of the shirt material he buys 2 metres of the trouser material. He sells the materials at 12% and 10% profit respectively. His total sale is ` 36,600. How much trouser material did he buy?

Ans. Let ratio between shirt material and trouser material be

The cost of shirt material =

The selling price at 12% gain =

= =

The cost of trouser material =

The selling price at 12% gain =

= =

According to the question,

= 100 meters

Now, trouser material = =

= 200 meters

Hence, Hasan bought 200 meters of the trouser material.

8. Half of a herd of deer are grazing in the field and three fourths of the remaining are playing nearby. The rest 9 are drinking water from the pond. Find the number of deer in the herd.

YOU WILL COMPLETE THIS AS HW

BUT, I WILL EXPLAIN YOU HOW TO START

the number of deer

so, let the the number of deer be x

Half of a herd of deer are grazing in the field

so. no. of deer grazing in the field = x/2

three fourths of the remaining are playing nearby

remaining deer = x-x/2 =x/2

so, no. of deer playing nearby =3/4(x/2)

no. of deer drinking water from the pond.=9

now, no. of deer grazing in the field +no. of deer playing nearby+no. of deer drinking water = total no. of deer

=> x/2 +3/4(x/2) +9 =x