Finding the Unknown | FIO

Question 6

The weight of a brick is 1 kg more than half its weight. What is the weight of the brick?

Solution

We will use a variable to represent the unknown weight and form an equation to solve it.

Step 1 — Setting up the Equation

We need to find the weight of the brick. Let us call the weight of the brick 'x' kilograms. The problem tells us something about this weight. It says the weight of the brick is equal to half its weight plus 1 kg. We can write this as an equation. Weight of the brick = Half its weight + 1 kg

$x = \frac{x}{2} + 1$

$\boxed{x = \frac{x}{2} + 1}$

Diagram 1

Step 2 — Solving the Equation

Now we need to find the value of 'x'. We want to get all 'x' terms on one side of the equation. Let us subtract $x/2$ from both sides. This keeps the equation balanced.

$x - \frac{x}{2} = \frac{x}{2} + 1 - \frac{x}{2}$

On the left side, $x - x/2$ is like 1 whole minus half. This leaves half. So, $x - x/2$ becomes $x/2$ . On the right side, $x/2 - x/2$ becomes 0. So, only 1 is left on the right side.

$\frac{x}{2} = 1$

Now, we have $x/2$ equals 1. To find 'x', we need to multiply both sides by 2. This will remove the division by 2 on the left side.

$\frac{x}{2} \times 2 = 1 \times 2$

On the left side, the 2 in the numerator and denominator cancel out. This leaves just 'x'. On the right side, $1 \times 2$ is 2.

$x = 2$

So, the weight of the brick is 2 kg.

Answer

(i) The weight of the brick is 2 kg.

More questions in FIO

Solve these equations and check the solutions.

(a) $3x - 10 = 35$ (b) $5s = 3s$ (c) $3u - 7 = 2u + 3$ (d) $4(m + 6) - 8 = 2m - 4$ (e) $\frac{u}{15} = 6$

Frame an equation that has no solution.

[Hint: 4 more than a number, and 5 more than a number can never be equal!]

Write 5 equations whose solution is $x = -2$ .

Find the value of each unknown:

(a) $2y = 60$ (b) $-8 = 5x - 3$ (c) $-53w = -15$ (d) $13 - z = 8$ (e) $k + 8 = 12 - k$ (f) $7m = m - 3$ (g) $3n = 10 + n$

I am a 3-digit number. My hundred's digit is 3 less than my ten's digit. My ten's digit is 3 less than my unit's digit. The sum of all the three digits is 15. Who am I?

The weight of a brick is 1 kg more than half its weight. What is the weight of the brick?

One quarter of a number increased by 9 gives the same number. What is the number?

Given $4k + 1 = 13$ , find the values of:

(a) $8k + 2$ (b) $4k$ (c) $k$ (d) $4k - 1$ (e) $-k - 2$

Fill in the blanks with integers.

(a) $5 \times \underline{\quad} - 8 = 37$

(b) $37 - (33 - \underline{\quad}) = 35$

Q10

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Q11

In the given picture, each black blob hides an equal number of blue dots. If there are 25 dots in total, how many dots are covered by one blob? Write an equation to describe this problem.

Q12

Here are machines that take an input, perform an operation on it and send out the result as an output.

Q13

What are the inputs to these machines?

Q14

A taxi driver charges a fixed fee of ₹800 per day plus ₹20 for each kilometer traveled. If the total cost for a taxi ride is ₹2200, determine the number of kilometres traveled.

Q15

The sum of two numbers is 76. One number is three times the other number. What are the numbers?

Q16

The figure shows the diagram for a window with a grill. What is the gap between two rods in the grill?

Q17

In a restaurant, a fruit juice costs ₹15 less than a chocolate milkshake. If 4 fruit juices and 7 chocolate milkshakes cost ₹600, find the cost of the fruit juice and milkshake.

Q18

Given $28p - 36 = 98$ , find the value of $14p - 19$ and $28p - 38$ .

Q19

The steps to solve three equations are shown below. Identify and correct any mistakes.

(a) $6x + 9 = 66$

$x + 9 = 11$

$x = 11 - 9$

$x = 2$

(b) $14y + 24 = 36$

$7y + 12 = 18$

$7y = 6$

$y = \frac{6}{7}$

$4x = 9x + 8 - 5$

$4x = 9x + 3$

$4x - 9x = 3$

$-5x = 3$

$x = \frac{-5}{3}$

Q20

Find the measures of the angles of these triangles.

Q21

Write 4 equations whose solution is $u = 6$ .

Q22

The Bakhshālī Manuscript (300 CE) mentions the following problem. The amount given to the first person is not known. The second person is given twice as much as the first. The third person is given thrice as much as the second; and the fourth person four times as much as the third. The total amount distributed is 132. What is the amount given to the first person?

Q23

The height of a giraffe is two and a half metres more than half its height. How tall is the giraffe?

Q24

Two separate figures are given below. Each figure shows the first few positions in a sequence of arrangements made with sticks. Identify the pattern and answer the following questions for each figure:

(a) How many squares are in position number 11 of the sequence? (b) How many sticks are needed to make the arrangement in position number 11 of the sequence? (c) Can an arrangement in this sequence be made using exactly 85 sticks? If yes, which position number will it correspond to? (d) Can an arrangement in this sequence be made using exactly 150 sticks? If yes, which position number will it correspond to?

Q25

A number increased by 36 is equal to ten times itself. What is the number?

Q26

Solve these equations:

(a) $5(r + 2) = 10$

(b) $-3(u + 2) = 2(u - 1)$

(d) $2(x - 4) = -16$

(e) $6(x - 1) = 2(x - 1) - 4$

(f) $3 - 7s = 7 - 3s$

(g) $2x + 1 = 6 - (2x - 3)$

(h) $10 - 5x = 3(x - 4) - 2(x - 7)$

Q27

Solve the equations to find a path from Start to the End. Show your work in the given boxes provided and colour your path as you proceed.