# Calculator skills for O level math

These skills in using the calculator fx-96 SG PLUS are useful to check your answers in O level Amaths and Emaths:

1. Round off to number of decimal places (Fix)
2. Round off to number of significant digits (Sci)
3. Using the memory A, B, C, D, E, X, Y to store the answers for intermediate steps so the final answer is accurate
4. Using statistics mode to calculate the mean and standard deviation (for both grouped and ungrouped data)
5. Using statistics mode A+BX linear regression to calculate the intercept and gradient of transformed linear graph. ( When keying in the data, do not key in the data that you ignored in your graph plotting)
6. Using DRG to convert between radians and degrees
7. Using fraction to determine Highest Common Factor
8. Solving simultaneous linear equations of 2 to 3 unknowns, quadratic and cubic equations of 1 unknown
9. Finding the gradient of a curve with known equation without differentiating, or checking the differentiation results by substituting a small number such as 0.001 as delta x.
Gradient or dy/dx = [f(x+ delta x)- f(x)]/ (delta x)

Eg. Find the gradient of the curve for y = (2x^2 – 1/x) at x=3
Find y at x= 3.001. Call it f(b)
Find y at x = 3. Call it f(a)
Gradient at x = 3 = [f(b)- f(a)] / 0.001

f(b) = 2 X 3.001^2 – 1/3.001 = 17.6788
f(a) = 2 X 3 ^2 – 1/3 = 17.6667

[f(b)-f(a)] / 0.001 = 12.1 (3 sig fig)

Compared with differentiation

dy/dx = 4x + 1/x^2
gradient at x= 3, = 109/9 = 12.1 (3 sig fig)

For Emaths students who have not learnt differentiation, the calculator approach is an alternative way to check the gradient.