Imagine you are a 1940s RAF pilot flying on one of the most famous raids of World War Two.
Your crew has to calculate the precise position at which to drop a bomb which could prove a significant morale booster in the four-year-old war with Germany. Where do you drop it?
This was the scenario facing pupils at a Hampshire comprehensive under an imaginative but controversial attempt to enliven lessons by looking at the maths behind the 1943 Dambusters raids.
Peter Ransom, a maths teacher at Mountbatten school in Romsey, with a penchant for using historical events to fire pupils' interests in the subject, was captivated by the 60th anniversary of the raids last year.
He read up on the missions, portrayed famously in the 1954 film starring Michael Redgrave in which three dams on the Ruhr were breached using a newly-invented bouncing bomb.
Then he dressed up as a 1940s RAF navigator, heading off to a lesson with Year 11s via the school staffroom, where colleagues' jaws dropped.
Among the tasks the pupils were given were to work out how to ensure the bomber was flying the requisite 60 feet above the ground, from where the bombs should be dropped.
They were then asked to draw on a diagram the position and angle at which the bomb should be dropped.
Mr Ransom showed them a demonstration of the raids, which he had programmed into a graphic calculator, followed by a clip from the 1954 film of the raids.
He said the lesson had been a way of livening up teaching for pupils about to embark on GCSE revision last year. It had proved so popular that he had had since taught it at several Saturday morning "masterclasses" to children from other schools.
He said: "The children really enjoyed it. At one of the masterclasses, one came up to me afterwards and said it was the best thing he had ever done in maths."
The Dambusters raids of May 16 1943, blew up three dams and resulted in an estimated 1,294 people drowning. Fifty-three aircrew were killed.
Mr Ransom, who was presenting the lesson at the Mathematical Association's annual conference in York this week, said he was conscious of the need to treat the subject sensitively. He did stress to youngsters that while the mission had been a big morale booster to the British, it had led to "appalling" loss of life.
In the past, he has used other historical events to enliven lessons. For example, he dressed up as the 17th-century mathematician John Blaygrave for a lesson about sundials.
But there was a scathing response when The TES contacted the German embassy in London.
Ludwig Linden, its spokesman, said: "As a parent, if I heard about using this as a vehicle for teaching maths, I would say 'think again'.
"This lesson has its base in history and I am not saying skip over that.
But it does tend to cement the old stereotypes about Germany, and to discourage students from learning about the new Germany. As a parent, I would very much object to that."