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Jo buys some apples. She uses the formula
Cost of apples = (Cost of one apple)*(number of apples bought)
The cost of one apple is 23p.
In order to work out the cost of 4 apples, you need to multiply 23p with 4.
Cost of 4 apples = 23*4 = 92p.
Therefore, the cost of 4 apples bought by Jo is 92p.