So, the context is as follows.

Inside the huge temple premises, there is a Vinayagar (Ganapathi) shrine. Asper royal decree of the founder emperor of the Brihadeeshwara temple, Raja RajaChola I, every day, 150 bananas were to be served to devotees! Since the Cholasfollowed the lunar calendar which has 360 days a year (30 days in 12 months) 54,000 bananas had to be served every year.

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Now, the currency used during the Chola period was called 'Kasu', which couldbuy 1200 bananas. So, 45 Kasus were needed every year!

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The emperor, as the chief patron of the temple, could have easily donated 45 Kasus every year. But instead of doing that, he allocated 360 Kasus towards the temple trust, and facilitated arrangements between the temple trust & fourprominent, trustworthy & capable merchant guilds, so that the guilds tookthe 360 Kasus as a loan from the temple trust, invested in their businesses,did trade & commerce in India & abroad, returned 12.5% interestannually, and retained the remaining as profit!

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12.5% interest on 360 Kasus came to 45 Kasus, which is what the 'banana arithmetic' required!

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So, the treasury of the royalty acted as a CSR wing of the empire, facilitating both commerce & philanthropy in a smart way!

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The inscriptions on the walls of the Ganapathy temple of the Thanjavur Brihadeeswara temple mention the details of this banana arithmetic, along with the names of merchant guilds & a ton of other details!

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Wow! How fascinating!

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