The remainder when $428^{2024}$ is divided by 21 is__________

The remainder when $428^{2024}$ is divided by 21 is__________

Solution

$\begin{aligned} & (428)^{2024}=(420+8)^{2024} \\ & =(21 \times 20+8)^{2024} \\ & =21 \mathrm{~m}+8^{2024} \end{aligned}$
Now $8^{2024}=\left(8^2\right)^{1012}$ $\begin{aligned} & =(64)^{1012} \\ & =(63+1)^{1012} \\ & =(21 \times 3+1)^{1012} \\ & =2 \ln +1 \end{aligned}$ $\Rightarrow$ Remainder is 1.

Asked in: JEE Main 2024 (09 Apr Shift 1)

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