In 2020, the production of foodgrain A increased over 2019 by the same percentage as in 2019 over 2018, and the production of foodgrain C in 2020 increased by 35% over 2019. If the export of both foodgrains was 40% of their respective production in 2020, then what was the total domestic consumption (in million tonnes) of these two foodgrains in that year?

The percentage increase in the production of foodgrain A in 2019 over 2018 will be $$\dfrac{450-400}{400}\times 100 = \dfrac{100}{8}\%$$

Therefore, the production of foodgrain A in 2020 over 2019 will be $$450\times \left(1+\dfrac{100}{800}\right)= 506.25$$

And the total Exports will be $$506.25\times \dfrac{40}{100} = 202.5$$

And the Domestic consumption will be $$506.25-202.5=303.75$$

The production of foodgrain C in 2020 will be $$325\times \left(1+\dfrac{35}{100}\right)= 438.75$$

And the total Exports will be $$438.75\times \dfrac{40}{100} = 175.5$$

And the Domestic consumption will be $$438.75-175.5= 263.25$$

Therefore, the total Domestic consumption for A and C in 2020 will be $$263.25+303.75 = 567$$