Answer:
20 hours
Step-by-step explanation:
We can work easier if we think in terms of an hour
the first equation that we can write is
A + B = 1/4 (its meaning is that in an hour A and B fill 1/4 of the cistern)
the second equation we can write is
A + C = 1/5 (its meaning is that in an hour A and C fill 1/5 of the cistern)
the third equation that we can write is
B = 2C (its meaning is that in an hour B fill 2 times C the cistern)
now we can substitute the value of B in the first two equations
A + 2C = 1/4
A + C = 1/5
A = 1/5 - C
1/5 - C + 2C = 1/4
C = 1/4 -1/5
C = (5-4)/20
C = 1/20 (this means that in an hour C will fill 1/20 of the cistern, so it takes 20 hours to fill the entire cistern)
A = 1/5 - 1/20
A = (4-1)/20 = 3/20
B = 1/20 *2 = 1/10
Answer:
84
Step-by-step explanation:
28x3=84
I hope i did that right
please give me Brainliest you dont have to tho
Answer:
Primul copil are 6 lei, al doilea are 12 lei, al treilea are 27 de lei.
Step-by-step explanation:
Lăsați suma primului copil să fie x.
Lăsați suma al doilea copil să fie y.
Lăsați suma al treilea copil să fie z.
Trei dintre ei au 45 de lei în total.
Aceasta înseamnă că:
x + y + z = 45 ________(1)
Al doilea are de două ori valoarea primului:
y = 2x
Al treilea are cu 15 lei mai mult decât al doilea:
z = 15 + y
=> z = 15 + 2x
Puneți valoarea y și z în (1):
x + 2x + 15 + 2x = 45
5x = 45 - 15 = 30
x = 30 / 5 = 6 lei
=> y = 2 * 6 = 12 lei
=> z = 15 + 12 = 27 lei
Primul copil are 6 lei, al doilea are 12 lei, al treilea are 27 de lei.