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Future perfect
I'll have approximated you'll have approximated he'll have approximated we'll have approximated you'll have approximated they'll have approximated
Future perfect continuous
I'll have been approximating you'll have been approximating he'll have been approximating we'll have been approximating you'll have been approximating they'll have been approximating
I'd be approximating you'd be approximating he'd be approximating we'd be approximating you'd be approximating they'd be approximating
Past
I'd have approximated you'd have approximated he'd have approximated we'd have approximated you'd have approximated they'd have approximated
Past continuous
I'd have been approximating you'd have been approximating he'd have been approximating we'd have been approximating you'd have been approximating they'd have been approximating