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‎In this article‎, ‎first of all‎, ‎the Kumaraswamy distribution is introduced‎. ‎Then‎, ‎the joint and marginal distributions of W = X1/X2 and T = X1/X1+X2 where X1 and X2 are independent Kumaraswamy random variables‎, ‎are obtained and the moments of these random variables are computed‎.

‎The distribution of random variables  W  and T  can be used in reliability studies and statistical models such as stress-strength‎.

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The cumulative distribution and density functions of a product of some random variables following the power distribution with different parameters have been provided.
The corresponding characteristic and moment-generating functions are also derived.
We extend the results to the exponential variables and furthermore, some useful identities have been investigated in detail.

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Drought is one of the most important concepts in hydrology, which has gained increased significance in recent years,
and the results of its modeling and analysis are crucial for risk assessment and management. This study examines drought at
the Zahedan station during the statistical period from 1951 to 2017 using the standardized precipitation index and explains
multivariate data modeling methods using Vine Copulas. Various models are compared using goodness-of-fit criteria, and
the best model is selected. Additionally, joint return periods are calculated and analyzed.