Question

A
30% din ce nr reprezintă 27?
B
Sa se afle un nr stiind ca 12% din el reprezintă 3,6.
C
Daca 0,5% dintr-un nr reprezintă 15, sa se afle nr . Dau coroana va promit

Answer 1

a)
30℅×x=27
30/100×x=27
x= 27÷3/10
x= 27×10/3
x=90

b)
12℅×x= 3,6
12/100×x= 3,6
x= 3,6:3/25
x= 3,6×25/3
x=30

c) 0,5℅×x= 15
0,5/100×5=15
x= 15÷0,5/100
x= 15×100/0,5
x= 3000

Answer 2

A

a- număr

30%·a=27

$\dfrac{30a}{100}=27$

$\dfrac{3a}{10}=27$

3a=10·27

3a=270=>a=$\dfrac{270}{3}=90$

B

a- număr

12%·a=3,6

$\dfrac{12a}{100}=3,6$

$\dfrac{3a}{25}=\dfrac{36}{10}$

$\dfrac{3a}{25}=\dfrac{18}{5}$

15a=450=>a=$\dfrac{450}{15}=30$

C

a- număr

0,5%·a=15

$0,5=\dfrac{5}{10}=\dfrac{1}{2}$

$\dfrac{\dfrac{1}{2}}{100}a=15$

$\dfrac{\dfrac{1}{2}}{100}=\dfrac{1}{2}\cdot \dfrac{1}{100}=\dfrac{1}{200}$

$\dfrac{1}{200}a=15$

$\dfrac{a}{200}=15$

a=200·15=3000