Fractions to decimals - help!

(18 Posts)

DD is in year 7 and has to answer the following for 1 mark in a test:

Write a decimal with a value between 4/7 and 5/7

Totally stumped - it can't be hard if its only worth 1 mark right???

doublecakeplease Mon 14-Jan-13 22:26:01

Any 4 point something divided by 7

So 4.2 / 7 etc.

4/7 is the same as 8/14
5/7 is the same as 10/14

(Both top and bottom have been multiplied by 2)

Therefore 9/14 is a fraction between 4/7 and 5/7 and is the same as 4.5/7 but I assume your DD would be expected to express it a just a fraction.

galwaygirl Mon 14-Jan-13 22:48:14

What double cake said except to continue it on to express as a decimal 4.2/7 = 0.6

doublecakeplease Mon 14-Jan-13 22:51:44

Sorry - forgot the answer!!thanks Gal :-) Fraction to decimal is always numerator (top number) divided by the denominator.

Would your DD be allowed a calculator for this? I would just put 4/7 in the calculator (0.57142) and 5/7 in the calculator (0.71428) and then pick a decimal between the two e.g. 0.65.

Whoops forgot the decimal bit! smile

Divide the top number in my example by the bottom number so 9/14=0.64

sashh Tue 15-Jan-13 06:44:04

that / line, or the one with the line and two dots means 'divide by'.

4/7 = 0.57 (don't bother with the whole thing)
5/7 = 0.71

Find a number betwee 0.57 and 0.71 so 0.6, 0.65, etc etc

sashh Tue 15-Jan-13 06:53:10

Or she could just pick a number between 4 and 5 and divide that by 7.

That would be easier.

Thanks everyone . She's not allowed a calculator and I go blank whenever I think of 4.5 divided by 7 - is there an easy way to do this?

doublecakeplease Tue 15-Jan-13 21:50:12

Draw a long division box with 4.2 inside and 7 outside.

Mimic the decimal point above the original - in the answer space iykwim

Say 'how many 7s divide into 4? = 0. So the zero sits infront of the decimal on the answer line

The 4 still needs to be used so it moves to sit with the 2 to make 42.

How many 7s in 42?? = 6 so 6 sits after the decimal point on the answer line making the answer 0.6

comfysofas Sat 20-Apr-13 10:16:19

Found this website through another poster it helps me with lots of stuff.

mccandjt Mon 20-May-13 14:29:39

Message deleted by Mumsnet for breaking our Talk Guidelines. Replies may also be deleted.

StealthOfficialCrispTester Mon 20-May-13 14:31:03

Woolly is right abd that is the easy way. You shouldnt be writing 4.5/7 as yiure mixing decimals with fractikns

StealthOfficialCrispTester Mon 20-May-13 14:33:09

Ah sorry but she has to write it as a decimal. In that case id take woolys answrr and convert it to a decimal

You coukd akso say 4/7 equaks 40/70. 5/7 is 50/70. Therefor an in etween would be 45/70. Which is 9/14 again

StealthOfficialCrispTester Mon 20-May-13 14:34:04

Or 41 over 70 or 42 etc. Infinite possibilities. But 45 seems the obvious one

drwitch Mon 20-May-13 14:39:50

the best thing is to muliply by 10 and then find a number that is divisible by 7
then you can simplify the faction into something over 10

4/7 = 40/70 5/7 = 50/70
42/70 and 49/70 are both between 40/70 and 50/70
42/70 = 6/10 49/70 = 7/10
6/10 =0.6
7/10 = 0.7
easy if you know your tables

StealthOfficialCrispTester Mon 20-May-13 14:40:50

Oohyes of ciurse

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