Squares and Square Roots | FIO

Question 13

Find the sidelength of a rhombus whose diagonals are of length 24 units and 70 units.

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Solution

We can find the side length of the rhombus by using its properties and the Pythagorean theorem.

Step 1 — Finding the lengths of half-diagonals

A rhombus is a special type of quadrilateral where all four sides are equal. Its diagonals cut each other exactly in half. They also meet at a perfect right angle (90 degrees).

Let the two diagonals of the rhombus be d1d_1 and d2d_2. We are given their lengths as 24 units and 70 units. So, d1=24d_1 = 24 units and d2=70d_2 = 70 units.

When the diagonals bisect each other, they form four smaller right-angled triangles inside the rhombus. The legs of these triangles are half the lengths of the diagonals.

Let the half-length of the first diagonal be h1h_1. h1=d12h_1 = \frac{d_1}{2} h1=242h_1 = \frac{24}{2}

h1=12 units\boxed{h_1 = 12 \text{ units}}

Let the half-length of the second diagonal be h2h_2. h2=d22h_2 = \frac{d_2}{2} h2=702h_2 = \frac{70}{2}

h2=35 units\boxed{h_2 = 35 \text{ units}}

Diagram 1

Step 2 — Using the Pythagorean Theorem

Each of the four triangles formed by the diagonals is a right-angled triangle. The sides of the rhombus are the hypotenuses of these triangles.

Let 'a' be the sidelength of the rhombus. In one of these right-angled triangles (for example, triangle AOD), the two shorter sides (legs) are h1h_1 and h2h_2. The longest side (hypotenuse) is 'a'.

The Pythagorean theorem states that in a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides. So, a2=h12+h22a^2 = h_1^2 + h_2^2.

a2=122+352a^2 = 12^2 + 35^2

First, we calculate the squares of the half-diagonals. 122=12×12=14412^2 = 12 \times 12 = 144 352=35×35=122535^2 = 35 \times 35 = 1225

Now, we add these values together. a2=144+1225a^2 = 144 + 1225 a2=1369a^2 = 1369

To find 'a', we need to calculate the square root of 1369. a=1369a = \sqrt{1369}

a=37 units\boxed{a = 37 \text{ units}}

The sidelength of the rhombus is 37 units.

Answer

The sidelength of the rhombus is 37 units.

More questions in FIO

Q1

Earlier, we saw a method to create a square with double the area of a given square paper. There is another method to do this in which two identical square papers are cut in the following way.

Can you arrange these pieces to create a square with double the area of either square?

Q2

The length of the two equal sides of an isosceles right triangle is given. Find the length of the hypotenuse. Find bounds on the length of the hypotenuse such that they have at least one digit after the decimal point.

(i) 3

(ii) 4

(iii) 6

(iv) 8

(v) 9

Q3

The hypotenuse of an isosceles right triangle is 10. What are its other two sidelengths? [Hint: Find the area of the square composed of two such right triangles.]

Q4

If a right-angled triangle has shorter sides of lengths 5 cm and 12 cm, then what is the length of its hypotenuse? First draw the right-angled triangle with these sidelengths and measure the hypotenuse, then check your answer using Baudhāyana's Theorem.

Q5

If a right-angled triangle has a short side of length 8 cm and hypotenuse of length 17 cm, what is the length of the third side? Again, try drawing the triangle and measuring, and then check your answer using Baudhāyana's Theorem.

Q6

Using the constructions you have now seen, how would you construct a square whose area is triple the area of a given square? Five times the area of a given square? (Baudhāyana's Śulba-Sūtra, Verse 1.10)

Q7

Let aa, bb and cc denote the length of the sides of a right triangle, with cc being the length of the hypotenuse. Find the missing sidelength in each of the following cases:

(i) a=5,b=7a = 5, b = 7

(ii) a=8,b=12a = 8, b = 12

(iii) a=9,c=15a = 9, c = 15

(iv) a=7,b=12a = 7, b = 12

(v) a=1.5,b=3.5a = 1.5, b = 3.5

Q8

Find 5 more Baudhāyana triples using this idea.

Q9

Does this method yield non-primitive Baudhāyana triples?

[Hint: Observe that among the triples generated, one of the smaller sidelengths is one less than the hypotenuse.]

Q10

Are there primitive triples that cannot be obtained through this method? If yes, give examples.

Q11

Find the diagonal of a square with sidelength 5 cm.

Q12

Find the missing sidelengths in the following right triangles:

Q13

Find the sidelength of a rhombus whose diagonals are of length 24 units and 70 units.

Q14

Is the hypotenuse the longest side of a right triangle? Justify your answer.

Q15

True or False—Every Baudhāyana triple is either a primitive triple or a scaled version of a primitive triple.

Q16

Give 5 examples of rectangles whose sidelengths and diagonals are all integers.

Q17

Construct a square whose area is equal to the difference of the areas of squares of sidelengths 5 units and 7 units.

Q18

(i) Using the dots of a grid as the vertices, can you create a square that has an area of (a) 2 sq. units, (b) 3 sq. units, (c) 4 sq.units, and (d) 5 sq. unit?

(ii) Suppose the grid extends indefinitely. What are the possible integer-valued areas of squares you can create in this manner?

Q19

Find the area of an equilateral triangle with sidelength 6 units. [Hint: Show that an altitude bisects the opposite side. Use this to find the height.]

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