Question

What is (3.5 x 10 to the fourth) to the second

Answer 1

So that is 3.5 times 10000 or 35000
then it is squared so 1,225,000,000 but to four significant digits it would be 1225 times 10^6 or on a online test 1225e+06

Answer 2

Exponents raised by exponents are resolved by multiplying the two exponents together . . . so distribute the exponent to the paranthesis

note:
3.5 = 3.5^1

(3.5 x 10^4)^2

(3.5^1*2 x 10^(4*2))

(3.5^2 x 10^8)

12.25 x 10^8

1.225 x 10^9