M+, M-, MRC use case

  Price Quantity
Coffee 10 13
Sugar 5 17
Milk 7 20

To calculate the total price press 10 * 13 M+ 5 * 17 M+ 7 * 20 M+ MRC. You’ll get 355.

% operation

What is 25% of 40? 40 × 25 %

If 10 is 25%. What is 100%? 10 ÷ 25 %

What is 40 + 25%? 40 + 25 %

40 - 25%? 40 – 25 %

MU operation

The product’s price is 100 after 20% discount. What’s the initial price? 100 MU 20 %.

Overflow error

12345678 × 1234 = returns ERROR 152.34566. The real result is 15234566652 but the calculator has only 8 digits, so it tries to say: 15234566???. ERROR flag means that overflow occurred during the calculation and the point after the third digit means that there are three unknown digits more.

Repeat the last operation

10 + 5 = The result is 15. Press = again and get 20. = ⇒ 25, and so on.

10 – 5 = ⇒ 5, again = ⇒ 0, = ⇒ -5, and so on.

24 ÷ 2 = ⇒ 12, = ⇒ 6, = ⇒ 3, = ⇒ 1.5.

Note #1. With multiplication, the trick works in another way. 2 × 3 = ⇒ 6, = ⇒ 12, = ⇒ 24. The result is multiplied by 2 (the first operand, not the second one, as for +, – and ÷ operations).

Note #2. You can’t repeat % and MU operations.

Counter (+=)

1 + = returns 1. Press = again and get 2, one more = will return 3 and so on. Note, that later you can type a new number and continue counting from it.

Power (×=)

2 × = ⇒ 4 (2²)

2 × = = ⇒ 8 (2³)

2 × = = = ⇒ 16 (2⁴)

or

2 × = × = ⇒ 16 (2⁴)

1/x (÷=)

10 ÷ = ⇒ 0.1

5 + 5 ÷ = ⇒ 0.1

2 × 3 + 4 ÷ = ⇒ 0.1

Change sign (–=)

5 – = will return -5. You can use it in expressions.

2 + 3 – = ⇒ -5

7 – 2 – = ⇒ -5

10 ÷ 2 – = ⇒ -5

WARNING: this trick doesn’t work if the last operation in the expression is multiplication:

1 + 2 × 3 – = the result is -4 while we expect -9.

Workaround: 1 + 2 × 3 + 0 – = ⇒ -9

Quadratic equations

ax²+bx+c=0

D=b²–4ac

x₁=(-b–√D)/(2a)

x₂=(-b+√D)/(2a)

A quick method of calculating √D and saving it to memory:

b × = M+ 4 × a × c M- MRC MRC √ M+ C/AC.

x₁: – b – MRC ÷ 2 ÷ a

x₂: – b + MRC ÷ 2 ÷ a

Fibonacci numbers

1 + = ⇒ 1

+ = ⇒ 2

+ = ⇒ 3

+ = ⇒ 5

+ = ⇒ 8