fastest way to calculate 1800/2.25

Question

I am ok with solving the problems but simple calculation such as 1800/2.25 slows me down by a lot. Do you have any fast and easy way to solve this division?

bhugi98 · Answer

1800/2.25=1800/(9/4)=1800*4/9=800

KarishmaB · Answer

Usually, converting decimals to fractions is advisable. Don't try to divide 1800 by 2.25. Convert 2.25 to fraction form: 2.25 = 225/100 = 9/4 (Note that both 225 and 100 are divisible by 25) It's good to know the multiplication tables as they help in quick calculations.

1800/(9/4) = 200*4 = 800

dabral · Answer

Another approach in case one does not want to turn 2.25 to 9/4. See the attached image.

Also, I wrote a blog post on how to deal with arithmetic manipulations on the GMAT:
https://www.gmatquantum.com/blog/how-to- ... tions.html

Cheers,
Dabral

Attachments

image23.png [ 18.15 KiB | Viewed 5755 times ]

JapinderKaur · Answer

I would second the suggestion of converting the decimal into fractions. But there's a quicker way of doing this conversion. 2.25 = 2+ 0.25 For the time-being, just consider the 0.25 bit. 0.25 =1/4. So, 2.25 = 2+ 1/4 = (8+1)/4 = 9/4 This is quicker than having to solve 225/100. I have given a few practice decimal-to-fraction conversions below. With some more practice, the fraction equivalents of decimals will hopefully start flashing in your mind automatically.

Practice Decimal-to-Fraction Conversions i) 3.75 ii) 4.67 iii) 9.125 iv) 7.33 v) 8.17 SOLUTIONS i) 0.75 = 3/4 So, 3.75 = 3+3/4 = 15/4 You don't need to go the 375/100 route. That will take longer. ii) 0.67 = 2/3 So, 4.67 = 4+ 2/3 = 14/3 iii) 0.125 = 1/8 (no need to learn this by rote. Just think: 0.125 is half of 0.250, and so, half of 1/4) So, 9.125 = 9+1/8 = 73/8 iv) 0.33 = 1/3 So, 7.33 = 7+ 1/3 = 22/3 v) 0.17 is close to 0.167, which is the half of 0.33. So, 0.167= 1/6. 8.17 = 8+1/6 = 49/6 I hope this helps.

rajatjain14 · Answer

It would be best if you can memorize these commonly used decimals for quicker calculations: 
   \frac{1}{2} = 0.5  
  \frac{1}{3}= 0.333  
  \frac{1}{4} = 0.25  
  \frac{1}{5} = 0.2  
  \frac{1}{6}= 0.1667  
  \frac{1}{7} = 0.1429  
  \frac{1}{8} = 0.125  
  \frac{1}{9} = 0.111  
  \frac{1}{10} = 0.1

Practice Problems: 
   4.67 = 4+2*\frac{1}{3}= \frac{14}{3}  
  2.25 = 2+\frac{1}{4} = \frac{9}{4}  
  6.125 = 6 +\frac{1}{8} = \frac{49}{8}  
  3.22 = 3 + 2*\frac{1}{9}= \frac{29}{9}

Regards,
Rajat

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fastest way to calculate 1800/2.25

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