Question

One kilogram of onions cost Rs 12.75. How much will 3.5 kg cost?

Answer 1

Hint: When costs of one item is given, and question is to find the costs of many items, that can be understood by following simple example :
                                           one pen costs = 5 rupees
                                Then two pens costs = (5 + 5) rupees = 10 rupees
                                                                                                    $ \Rightarrow 2 \times 5$
                             Then three pens costs = (5+5+5) rupees = 15 rupees
                                                                                                    $ \Rightarrow 3 \times 5$
                                              costs of pens = numbers of pens $ \times $costs of one pen
i.e. costs of numbers of item = numbers of item $ \times $costs of one item

Complete step by step solution:
Step 1
Cost of one kilogram of onions = 12.75 rupees

Step 2
$\therefore $ Cost of 3.5 kg of onions = amount of onions $ \times $cost of one kilogram of onions
                                                $ = {\rm{ }}3.5{\rm{ }} \times {\rm{ }}12.75$
                                                = $44.625$ rupees

Therefore, The cost of 3.5 kg of onions is 44.625 rupees.

Additional information: Rupees is national currency. In India, we follow the Indian numeral system, the place values of digits go in the sequence of Ones, Tens, Hundreds, Thousands, Ten Thousand, Lakhs, Ten Lakhs, Crores and so on.

Note:
These types of questions can also be solved using the unitary method, we have to find the amount needed for one unit of the substance and then we multiply by the quantity provided.
For example : a box contain 10 chocolates (let's write this sentence in mathematical form)
i.e. 1 box = 10 chocolate,
then number of chocolates in 3 boxes can be found by unitary method
i.e. 3 boxes = 3$ \times $10 = 10 chocolates
Alternate method: Unitary method
The unitary method is a technique for solving a problem by first finding the value of a single unit, and then finding the necessary value by multiplying the single unit value.
1 kg of onion = 12.75 rupees
3.5 kg of onions $ = 3.5 \times 12.75 = 44.625$ rupees