43% of the analysed 14943 responses were correct, and the errors made were depressingly familiar:
8.1% were numerically correct but expressed to the nearest order of magnitude not to 1 significant figure.
3.1% were numerically correct but expressed to 2 significant figures.
In 2.9% of responses, the square root on the numerator had only been applied to the first number (4 in the example shown)
2.9% had used 10 to the plus 6 instead of 10 to the minus 6 in the denominator (which may have been caused by dividing rather than multiplying by 10 to the minus 6).
So it remains the simple things that cause the problems. Sig figs, calculator use, precedence…