First published in 1967, this was the Metric edition that followed in 1971, the year before I
I remember these books so well because they were so different from anything else in that their focus was on getting children to truly understand the math they were learning. This was toward the end of the New Math era that began quietly after WWII and rose to a crescendo of discontent at the end of the 1970s. My teaching experience in a fourth grade class in Bristol in the UK from 1972 to 1977 coincided with the start of the back to basics movement and the disillusionment of the math reform movement which was characterized by the mystical set theory of number that virtually no-one could fully understand.
If only we had realized back then that young children still need to remember certain math facts to go along with their deeper understanding perhaps the current math reform movement would stand a better chance of succeeding.
Sadly, I don't think the cry of "back to basics" will ever go away, as misguided as it continues to be.