David cuts a cake into two equal halves. He cuts one half into smaller pieces of equal size. Each of these smaller pieces weighs twenty grams. If he has seven pieces of the cake in all, how heavy is the original cake?
240 grams
Let the weight of original cake be x.
Then the weight of one half is x2.
There are a total of seven pieces. ⇒ The number of smaller pieces = 6.
As each of the smaller piece weighs 20 grams, the weight of one half is 20 × 6 = 120 grams.
Hence the total weight of the cake = 2 × 120 = 240 grams.