If the objective is to know how much was the percentage increase or discount of an amount, the mathematics teacher Giuseppe Nobilioni, from the Objective course, explains: the first step is to divide the final amount by the initial amount. If the result of the division is greater than 1, there was growth; less than one, there was retraction.

# How to check the increase of a product in Percentage %

A product cost R$ 820. Months later, it costs R$ 960. How much was the increase?

Dividing the final value by the initial value:

960/820 = 1.17 => Which, passing the denominator to the other, in the language of mathematics would be the same thing as saying 960=1.17,820, right?

Considering the rule explained above (in the table “Summary of the rule on how to calculate a new value with an increase in %”, multiplying by 1.17 is the same as saying that there was an increase of 17%.

**Summary:** if the price went from 820 to 960 and the 960/820 division gives 1.17, there was an increase of 17%

# How to check a product's discount in % Percentage

One price was R$ 600 and drops to R$ 420. How much is the discount?

Dividing the final value by the initial value:

420/600 = 0.7 => Which, passing the denominator to the other, in the language of mathematics would be the same thing as saying that 420 = 0.7 x 600

Again, considering the explanation in the table “Summary of how to calculate a new value with a reduction/discount in %”, multiplying by 0.7 is the same as saying that there was a reduction of 30%.

**Summary:** if the price went from 600 to 420 and the division gives 0.7, it means that there was a discount of 30%

# Now follows a little program in Language c that checks what was the increase or discount of a product in Percentage %

#include #include main(){ while(1){ float vi,vf,d; printf("\n\tCALCULATES THE INCREASE OR DISCOUNT OF A PRODUCT ON %%\n"); printf("\n\tEnter the initial product value: "); scanf("%f",&vi); printf("\tType the final product value: "); scanf("%f",&vf); d=vf/vi; if(vi>vf){ d = (1-d) *100; printf("\nDiscount was from: %f%%\n\n", d); } else { d = (d*100)-100; printf("\nThe product had an increase of: %f%%\n\n", d); } system("pause"); system("cls"); } }

If you wish, download the executable program that makes this calculating the increase or discount of a product's value in percentage automatically.

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