The number $3 \times 15 \times 11 + 11$ is a . . . . . . number.

Explain why $7 \times 11 \times 13+13$ and $7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1+5$ are composite numbers.

$A$ positive integer is of the form $3q + 1$,where $q$ is a natural number. Can you write its square in any form other than $3m + 1$,i.e.,$3m$ or $3m + 2$ for some integer $m$? Justify your answer.

Why are the following numbers composite? Explain: $7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1 + 5$

The last digit of $2^5 \cdot 5^5$ is . . . . . . .

Write down the decimal expansion of the rational number $\frac{35}{50}$.