Number Puzzle
A number is multiplied by 3, and then 7 is added to the result. The final answer is the same as when the number is doubled and then increased by 10. What is the number?
A box of biscuits
A box of biscuits contains 36 biscuits. 20 biscuits have foil wrappers. 15 are chocolate biscuits with foil wrappers. If 9 are not chocolate and do not have a foil wrapper, then how many chocolate biscuits are there?
Let the unknown number be x.
ReplyDeleteThe number is multiplied by 3, then 7 is added:
3x + 7
The number is doubled, then increased by 10:
2x + 10
These two expressions are equal:
3x + 7 = 2x + 10
Solving for x:
Subtract 2x from both sides:
x + 7 = 10
Subtract 7 from both sides:
x = 3
So, the number is 3.