A fish tank is half full of water. If 10 gallons were added, the tank would be 7/8 full. What is the capacity of the tank (in gallons)?
A. 11 3/7
B. 22 3/7
C. 26 2/3
D. 30 3/8
E. 32 1/8
source: http://www.800score.com/gmat/
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7 comments:
If the adition of 10 gallons yields the transition from half tank (4/8) to 7/8 of the tank filled (a step of 3/8), then the total capacity is easily obtained as 10/(3/8) or 80/3. This number can be expressed in the form n m/3, and none of the other options with 7 or 8 in the denominator. In fact, (3, 7) and (3, 8) form twin prime pairs. Thus, the 80/3 results would never be expresseable in a form n m/7 or n m/8. The correct option can only be option C.
Can you try and explain that again in portuguese?
thank you!
If you try to add water to a full tank it will spill!!! :)
The correct question is:
A fish tank is half full of water. If 10 gallons were added, the tank would be 7/8 full. What is the capacity of the tank (in gallons)?
Francisco Saraiva, thanks. The word "half" was missing. I agree the "solution" is not as clear as required. Let me put it another way - but still in english, for the "world" to be able to follow our discussion:
10 gallons correspond to 3/8 of the tank, This results clearly from the enunciate. So the tank capacity is 10 gallons divided by 3/8 - which is 80/3. Such a rational number could never be expressed as a mixed number of type * */7 for the simple reason that 3 and 7 form a twin prime pair. The same reason holds for the form * */8. So, our only remaining option is answer C.
If X="Water Capacity", then:
X/2+10=(7/8)X <=> X=26.66(7)
Answer C.
JFD em PT:
o tanque inicialmente está a metade da sua capacidade máxima (1/2 ou 4/8). Ao adicionar 10gls passa a 7/8 logo os 10gls representam um aumento de 3/8.
Considerando x a capacidade do tanque:
10gallons = 3/8x, então x = 80/3
Para encontrar a opção correcta bastaria encontrar a opção expressa em n*m/3, e seria a opção C. No entanto surge nova questão:
80/3 = 26,7
26 2/3 = 17,3 os resultados n coincidem!!!!
Can someone please explain the inconsistency?? tnks
Nuno:
26 2/3 não é 26 vezes 2/3, mas sim 26 + 2/3 =26,(6)
Não existe sinal de multiplicar entre eles (nem sequer se está simplesmente a omitir).
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