Theory:

1. Nandhini bought \(3 \ m \ 40 \ cm\) of blue colour ribbon and \(4 \ m \ 50 \ cm\) of red colour ribbon. What was the total length of the ribbon bought by her?
 
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Solution:
 
Length of blue colour ribbon \(=\) \(3 \ m \ 40 \ cm\)
 
Length of red colour ribbon \(=\) \(4 \ m \ 50 \ cm\)
 
To find the total length, we need to add two quantities.
 
Total length of the ribbon \(=\) Length of blue colour ribbon \(+\) Length of red colour ribbon
 
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Therefore, the total length of the ribbon bought by Nandhini was \( 7 \ m \ 90 \ cm\).
 
 
2. Roshini bought \(4 \ m \ 20 \ cm\) of blue colour ribbon and \(2 \ m \ 50 \ cm\) of red colour ribbon. What was the difference between the length of two colour ribbons?
 
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Solution:
 
Length of blue colour ribbon \(=\) \(4 \ m \ 20 \ cm\)
 
Length of red colour ribbon \(=\) \(2 \ m \ 50 \ cm\)
 
To find the difference between the length of ribbons, we need to subtract two quantities.
 
Difference between the length of the ribbons \(=\) Length of blue colour ribbon \(-\) Length of red colour ribbon
 
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Therefore, the difference between the length of two ribbons was \(1 \ m \ 70 \ cm\).
 
 
3. A glass can hold \(300 \ ml\) of juice. How much litres of juice will be there in \(6\) glasses?
 
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Solution:
 
Quantity of juice a glass can hold \(=\) \(300 \ ml\)
 
Quantity of juices in \(6\) glasses \(=\) \(300 \ ml\) \(\times\) \(6\)
 
300×6¯1800¯
 
Quantity of juices in \(6\) glasses \(=\) \(1800 \ ml\)
 
We need to find the how much litres of juice can be held in \(6\) glasses, so convert \(ml\) to \(l\).
 
\(1000 \ ml\) \(=\) \(1 \ l\)
 
\(1 \ ml\) \(=\) 11000 \(l\)
 
\(1800 \ ml\) \(=\) 18001000 \(=\) 1.8 \(l\)
 
Therefore, \(6\) glasses can hold 1.8 litres of juice.
 
 
4. \(5\) \(kg\) of flour to be packed in a small packets, each packet can hold \(250 \ g\) of flour. How many packets are required to fill \(5 \ kg\) of flour?
 
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Solution:
 
Total quantity of flour \(=\) \(5 \ kg\)
 
Quantity of flour each packet can hold \(=\) \(250 \ g\)
 
Both numbers should be in the same units to do fundamental operations.
 
So, let us first convert \(kg\) to \(g\), to find the number of packets.
 
\(1 \ kg\) \(=\) \(1000 \ g\)
 
\(5 \ kg\) \(=\) \(5 \times 1000 = 5000 \ g\)
 
Number of packets required \(=\) \(\frac{\text{Total quantity of flour}}{\text{Quantity of flour each packet can hold}}\)
 
\(=\) 5000250
 
\(=\) 20
 
Therefore, 20 packets are required to pack \(5 \ kg\) of flour.
 
Important!
When we write measurement with different units:
 
The left side should be a higher unit
 
The right side should be a lower unit
 
Example: \(5 \ m \ 15 \ cm\)
 
Here, \(m\) is a higher unit and \(cm\) is a lower unit.