Chai pe charcha – Mathematics for amusement

There are two tea shops in the friendly neighbourhood around our office. Shop 1 has been our only option for coffee/tea for the last few years. We discovered shop 2 over the last couple of weeks. The taste of tea in both shops is comparable. However, the shape of the tea glasses amused me enough to spend some cognitive space on a scientific analysis.

The shapes of the tea glasses used by both shops are represented in Figure 1.

Figure 1 – shapes of tea glasses in shops 1 and 2

Glass 1 is shaped like a cylinder, glass 2 is shaped like the frustum of a right circular cone. The heights of both glasses are same. This observation led me to make some calculations of basic geometry. Figure 2 shows the schematic diagrams of glass 1 and glass 2.

Figure 2 – schematic geometrical diagrams of glasses 1 and 2

Calculation of Volumes:

Glass 1 –

Height h = 7 cm

Radius r = 2.5 cm

Volume of glass 1 = Volume of cylinder
= πr2h cm3
= 3.14 x (2.5)2 x 7 cm3
= 137 cm3

Glass 2 –

Height h = 7 cm

Radius r1 = 2.5 cm

Radius r2 = 2 cm

Volume of glass 2 = Volume of frustum of cone
= 1/3πh (r12 + r22 + r1r2) cm3
= 1/3 x 3.14 x 7 ((2.5)2 + 22 + 2.5×2)) cm3
= 112 cm3
Comparison of cost:

For the sake of calculation, let us equate the volume of the solid to the volume of the liquid it holds. Glass 1 holds 137 ml of tea and glass 2 holds 112 ml of tea. Shop 1 sells one glass of tea for 10 Rs, shop 2 sells one glass of tea for 7 Rs. Therefore shop 1 sells 13.7 ml of tea per rupee and shop 2 sells 16 ml of tea per rupee.

Mathematics tells us that drinking tea at shop 2 is more cost effective. The facts that shop 2 is just two doors down the road and delivers to our office form the icing on the cake.

Why go to all this trouble?

The decision to drink tea at one shop or the other is a matter of convenience and personal choice. Also, common sense can tell us which tea is more cost-effective. However, using basic Mathematics to arrive at this conclusion was a cognitive exercise that I thoroughly enjoyed.

Look around you. Find ways to use your subject knowledge to amuse yourself. Better still, encourage your children to do the same. The next time a child asks you, “where will I use all these mathematical formulae in my life?”, throw a similar problem for them to solve. When learning becomes amusing, you can’t draw the learner away from it.

We at NumberNagar® strive to connect concepts that children learn in schools to their everyday life. As facilitators, we take pleasure in practising what we preach. This is one part of my job that I love.


Image credits:

Featured image – Pixabay

Figure 1 – Reference 1 Reference 2



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Dr. Soumya Sreehari

Co-Founder and Specialist at NumberNagar®
Dr. Soumya is an Educator and Researcher with a passion for reading, writing and teaching. She holds a PhD in Chemistry (Michigan Technological University, Houghton, USA). Her experience as a student and a teacher in two countries led her to pursue a career in Education. Her core work at NumberNagar® involves quality delivery of product and services at every stage of the customer life cycle. She leads the team that makes this happen. Previously she has taught Chemistry to first year undergraduate students at Michigan Technological University. She is a voracious reader and challenges herself to read 50 books every year.

14 Replies to “Chai pe charcha – Mathematics for amusement”

  1. Wowwwwww…simply superb…I love math…but I never knew I can set an example like dis in our daily activities too…..ur just like young Sheldon….

  2. Wow Wow Wow! Being a mathematics learner myself and always wanting to show the esence of mathematics through reality , it truly amazes and inspires me to see this beautiful articulation and knowing that I have people around me who can help me achieve this way of communicating mathematics to the world. I bow to you ma’am.🙇🏻‍♀️

  3. Truly amazing! We blindly pick outlets to eat & drink but very rare do such thoughts come that are simple yet provoking!
    This was indeed an excellent approach – good to know that side too.

  4. Lovely way to compare.. liked it. I always wonder what is the use of all these formulas. I never enjoyed maths. May be now I shall start enjoying with my kids all over again.

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