At school sports day, the head teacher walks around the field and counts the number of relay teams entered so far this morning, calling this number \(x\). F...
Question 1 Report
At school sports day, the head teacher walks around the field and counts the number of relay teams entered so far this morning, calling this number \(x\). Four times this number, minus 9, equals 19. Solve \(4x - 9 = 19\) to find \(x\), the number of relay teams. (2)
Answer Details
This equation models a real count (the number of relay teams) using two operations, multiplying by 4 then subtracting 9; solving for \(x\) undoes these operations in reverse order.
\(4x - 9 = 19\)
\(4x = 28\) (adding 9 to both sides) [1 mark]
\(x = 7\) (dividing both sides by 4) [1 mark]
Checking by substitution, \(4(7) - 9 = 28 - 9 = 19\), confirms the value, and \(x = 7\) is also a sensible answer since the number of relay teams must be a whole number.
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